Between Physics and Metaphysics: Mulla Sadra on Movement 

  The concept of movement (harakat) lies at the heart of Mulla Sadra’s natural philosophy. His theory of substantial movement (al-harakat al-jawhariyyah) exposes many issues of classical philosophy to a new examination under the light of this highly complex and original concept. By allowing change in the category of substance, Sadra goes beyond the Aristotelian framework followed by the Peripatetics and the Illuminationists. In fact, by arguing rigorously for existential change in the substantial structure of physical bodies ,Sadra turns the classical concept of substance (jawhar) into a ‘structure of events’ and a ‘process of change,’ and abandons the erstwhile idea that substance is the ultimate building block of things. As we shall see, substance, for Sadra is not a ‘thing’ or ‘entity’ that exists in state of constancy. It is neither a purely physical entity in the sense of being a gross, dark, material body nor a purely non-physical and philosophical postulate. Hung between change and permanence, substance, like the rest of the world of nature, oscillates between existence and non-existence, thus displaying the infinitely dynamic play of the cosmos. Seen as such, Sadra’s cosmology contains no terms for dark and dead matter. On the contrary, in this perpetual play of the creative act of God, everything comes to be alive witnessing to the Divine breath that has been blown into them.

In this regard, Sadra’s cosmology in which the notion of movement occupies a central place is based on a qualitative understanding of nature. Nature, for Sadra, cannot be reduced to pure quantity because there is no such thing as pure quantity given the fact that every change in the world of nature, whether it is positional, spatial or temporal, is the outcome of an existential transformation in the very substance of things. The constant and perpetual movement in the world of ‘material’ entities makes the demarcation line between the living and the dead a blurred one, and Sadra takes special notice of this point. Instead of seeing the physical world in terms of machines and quantitative equations, Sadra puts emphasis on the qualitative dimension of nature: Nature displays an unmistakable vitality not because we like to see it that way but because it is in the very constitution of the physical realm to be in such an ‘existential journey’ towards the higher levels of being. It is, therefore, particularly important to notice the non-mechanical conception of nature espoused by Sadra’s cosmology especially since Sadra developed his theories at a time when the mechanistic understanding of nature was becoming the dominant way of looking at the world of nature in the West. The catastrophic consequences of the mechanistic world-view for the current environmental crisis are now obvious beyond a shred of doubt, and we are becoming more and more aware of the fact that the environmental crisis cannot be overcome by better engineering.

A veritable understanding of nature is the sine qua non of any attempts for the overcoming of this crisis, which is threatening not only the lives of trees and animals but also human beings. In this regard, Sadra’s cosmology in general and his theory of substantial movement in particular have direct relevance for this ongoing discussion.

The Aristotelian Framework: Movement as the Actualization of Potentiality

Following the scheme of Aristotelian physics, Sadra begins his discussion of movement by explaining the meaning of potentiality. The word potentiality (al-quwwah) is used in various meanings. The most common meaning is that power by which a living body does and displays certain actions. In this sense, potency is tantamount to power (al-qudrah), which makes a thing’s movement or action possible. A white dress, for example, has the possibility of becoming a black dress because it has potentiality in its physical constitution. But it needs an active agent to actualize this dormant potentiality. This, for Sadra, proves that a thing cannot be the source of change by itself and there must be an outside factor to induce it to change. Because if the source of a quality or a nature (ma‘na) in an entity were the thing itself, this would amount to an unchanging nature in that entity. The real nature of possible things, however, displays a different structure. Mulla Sadra takes this to mean that for every moving body there is a mover outside the thing itself.

The mover-moving relationship presents a hierarchical order just like in the case of causality. The issue here, however, is not mere casual relationship between two self-subsistent entities but rather a relationship of dependence. According to Sadra, whatever has priority and more intensity in existential realization (ashaddu taaassulan) is likely to be more a cause and less an effect. In this general sense, it is only God who is rightly entitled to be called the ‘cause’ of everything. On the other hand, prime matter (hayęla) has the least potentiality of being a cause because it is the weakest existentially.

After stating these preliminary points, Sadra begins his account of movement by saying that movement and rest (al-sukęn) resemble potentiality and actuality. In the general sense, i.e., according to the notion of passing form one place to another or from the state of possibility to that of necessity, they are both accidents of being-qua-being. Accordingly, being-qua-being is not in need of movement and rest unless it becomes the subject of natural or mathematical order.

An existing body capable of movement must bear some potentialities and some actualities simultaneously. A purely potential being cannot have any concrete existence as in the case of prime matter (al-hayęla). The state of a purely actual being, on the other hand, cannot apply to other than God who has no potentiality to be actualized. A being of such a nature should be a simple being which contains in itself everything. According to Sadra’s doctrine of being (wujęd), this refers ontologically to Being-qua-Being, and theologically to God. As for a contingent being capable of movement, it has the potentiality of gradual (tadrijin) transition from potentiality to actuality.

The actuality-aspect of a thing is that about which we are able to speak as a concrete reality in which the action of movement takes place.

The temporal term ‘gradual’ (tadrijin) in the definition of movement, however, has caused some problems for Muslim philosophers because the definition of movement as gradual transition from potentiality actuality implies that this process occurs in time. Although this statement is quite true in the ordinary use of language, the definition of time as the measure of movement leads to circularity. It was for this reason that some thinkers have come up with a new definition which contains no term of time. Relying on Ibn Sina, Suhrawardi and al-Razi, Sadra rebuts this objection by saying that the meaning of ‘sudden’, ‘gradual’ and the like is obvious with the help of the five senses. Moreover, says Mulla Sadra, there are a lot of clear and obvious things whose inner nature we can never fully know. Nevertheless this explanation did not satisfy the theologians (mutakallimęn), and they proposed the definition that movement is the realization of what is possible (mumkin al-husęl). Since we see here a step from potentiality to actuality, this realization points to a perfection. Thus, it is said that movement is a perfection for the moving body. But this perfection is necessarily different from other types of perfection because it has no real existence other than ‘passing to another place.’ Understood as such, a moving body possesses two special characteristics. The first is the inclination (tawajjuh) towards the targeted place (matlub) and the second is that there should remain something potential from the moving body. Therefore, the nature of movement is closely connected with the fact that there should remain some potentialities in things.

The foregoing considerations of movement lead to the following definition: movement is the first perfection for the potential being in so far as it is potential. This definition, says Sadra, goes back to Aristotle. Plato gives a similar definition. It is the coming out of the state of sameness, i.e., a thing’s being different from its previous state. Pythagoras proposes a close definition: It consists of alterity. After mentioning these definitions and their partial criticism by Ibn Sina Sadra states that all these different expressions refer to one and the same meaning, which is the change of the state of affairs in the moving body. In this respect Sadra criticizes Ibn Sina’s objection to Pythagoras that movement is not change itself but that by which change takes place. Sadra says that movement is not that by virtue of which change in things comes about but the change itself. Sadra pays particular attention to this point because it closely connected with the renewal of substantial natures (tajaddud al-akwan al-jawhariyyah) and continuously changing nature of things (taaawwul al-tyabi‘at al-sariyah).

Two Meanings of Movement

In al-Shifa Ibn Sina states that the word movement is used with two meanings: the first one is the passage (qat‘) view of movement according to which the moving body is taken as a present whole in its act of moving. When the mind comes to conceive the moving body with the points it passes over and leaves behind, it pictures these discrete points and time-instants as a present whole. But since this frozen picture proves nothing but a body extended in space and time as a continuous whole, this kind of movement exists only in the mind. The second kind is the medial movement (tawassut) according to which the moving body is always found somewhere between the beginning and end of the distance passed. This view actually refers to a state of continuation, viz. the body’s being at a point. As such, it does not allow any change and movement in the existential constitution of the thing but only a transposition from one place to another. It is this kind of movement that exists objectively in the external world.

Having no quarrel with the medial view of movement, Sadra sets out to prove the objective existence of the passage movement in the extra-mental world. He criticizes Ibn Sina and draws attention to a self-contradiction in Ibn Sina’s denial of the passage movement. Ibn Sina accepts time as something continuous in the external world because it can be divided into years, months, days and hours. It is the very definition of time, says Sadra, that corresponds to the passage movement. Upon this premise, Ibn Sina regards the passage movement as the locus and cause of time. But if the passage movement does not exist objectively how can it assume such a status? In other words, how can something non-existent be the locus of something existent?

Ibn Sina’s denial of the passage-view of movement results from his understanding of movement as an accident of things. A thing is a stable substance that exists in every instant of time insofar as it exists. But the movement has no existence in time-instants (an). If movement were one of the modalities of things, it would always have to be together with things. Movement exists in things only continuously (istimraran) which, in turn, refers to the second meaning. To this, Sadra replies that the locus of movement is not as a stable substance but the thing as the locus and place upon which an action is exercised. In order for a thing to receive movement and change, it should undergo some kind of change in its essential structure (darb min tabaddul al-ahwal al-haythiyyah). This is due to the principle that the cause of that which changes also changes (‘illat al-mutagayyir), and that the cause of that which is stable (‘illat al-thabit).

The main reason, however, for the denial of the passage movement is related to the very nature of this kind of movement, which Sadra describes as having weak existence. As the following quotation shows, ‘weak existence’ refers to existential dependence, namely to the fact that things of this sort are not self-subsistent and always caused by an agent:

‘Movement, time and the like belong to the category of things that have weak existence (da‘ifat al-wujęd). Accordingly, their existence resembles their non-existence, their actuality is similar to their potentiality, and their origination (hudęthuha) is nothing but their corruption (zawaliha). Each of these (qualities or attributes) requires the non-existence of the other; in fact their existence is their non-existence. Therefore, motion is the very destruction of a thing itself after it (is established in the physical world) and its origination before it (is actualized in the external world). And this mode (of being) is comparable to the absolute being in the sense that all relational beings (al-idafat) have some sort of existence. Likewise the existence of movement displays ambiguity/gradation (tashkik) and similitude (shabah) (of being close to both being and non-being).’

Within the framework of actuality-potentiality formulation, Sadra states that there are two poles of existence. The first is the First Reality or the Absolute Being, and the second is the first hyle. The former which contains no potentiality in and of itself is pure goodness par excellence, and the latter which is pure potentiality with no actual existence is evil containing in itself no goodness save accidentally. Nevertheless, since hyle is the potentiality of all beings, it has some share of goodness as opposed to non-existence (‘adam), which is pure evil. The hierarchy of existence stated in terms of pure actuality and pure potentiality provides a clue as to the structure of movement in the world of nature. By the same token, this shows, for Sadra, that a simple body is always composed of hyle and form because it has the potentiality of movement on the one hand, and ‘the material form’ (al-suat al-jismaniyyah) or a single continuous substance (al-ittisal al-jawhari), which is something actual on the other. According to Sadra, this aspect of physical substances proves, once more, the cardinal principle that ‘a simple reality (basit al-haqiqah) cannot but be the totality of everything’ (jami‘ al-ashya‘).

The Mover and the Moving Body

Aristotle had proposed his notion of the Prime Mover to terminate the infinite regression of casual chain in the world of nature. The most important consequence of this formulation is the stark distinction between the mover and the moving body—a complementary duality that was extended in posterity to positional movement. Now, seen from the perspective of vertical causality, every moving body needs a mover, and Sadra, following the Peripatetics, reformulates this relationship in terms of actuality and potentiality, as we have discussed before, actuality refers to the mover (al-muharrik), and potentiality to the moving body (al-mutaharrik). In other words, the mover as the actual being provides the cause of movement, and the moving body as the potential being stands at the receiving end of the process of movement.

This polarity, for Sadra, shows the impossibility of a single’s body’s being both the necessity of the existence of a prime mover to which all movement can ultimately be traced back. Sadra’s argument runs as follows: The moving body, in so far as it is a potential being, has to be a passive agent, i.e., the receiver of the act of movement, and the active agent namely the cause of movement, in so far as it is an actual being. These two qualities or aspects cannot be found in the same thing simultaneously due to the exclusive character of the two. In other words, a physical entity cannot be both the source and locus of movement at the same time. Here Sadra reaches the conclusion that all movement, in the light of the foregoing argument, should go back to an active agent which is ‘different form movement as well as from the locus (qabil) of movement, moving by itself, renewing itself by itself, and necessarily the source of all movement. And this (agent) has its own agent (i.e., principle) of movement in the sense of being the source of its continuous renewal. By this, I do not mean the instaurer (ja‘il) of its movement because instauration cannot exist between a thing and itself. This is so because the direct agent of movement has to be something in motion (mutaharrikan). Otherwise this would necessitate the difference of the cause (al-‘illah) from its effect (ma‘luliha). Thus, if this (chain of causation) does not end in an ontological agent (amr wujęd) which renews itself by itself, this would lead to regression or circularity.’

Sadra then continues to adduce proofs for the necessity of a prime mover for moving bodies. He rejects and replies some objections as follows. 1) If a thing were moving by itself, it would never reach rest because whatever endures by itself endures by its intrinsic qualities. Once these qualities or properties are disjoined from a thing, it no longer exists. 2) If a thing moving by itself, the parts of movement i.e. the subject of movement as a whole would be in rest, which means that the thing would  not move. 3) If the principle of movement were in the moving body itself, it would have no ‘fitting’ or natural place to which to could incline. According to the conventional definition of movement, however, if there were to be no natural place for a thing to which it could incline, it could not move either. 4) If a self-movement were a real property of the moving body, it would be a universal quality of ‘thingness’ (shay’iyyah) shared by all corporeal things. But this is not the case in natural order. In reality, says Sadra, movement is a particular quality provided by the outside mover. 5) Another proof for the impossibility of thing’s having the principle of movement in itself is that such a supposition would amount to the idea that both potentiality and actuality can be found in the same place simultaneously. If this were the case, actuality would not be succeeded by potentiality. Because according to the definition given above, movement is the first perfection for what is potential. If a thing were able to move by itself, it would be actual in all respects without leaving any room for potentiality, which is obviously inconceivable for contingent beings. 6) The relation of the moving body to movement is established through contingency (bi’l-imkan), and its relation to movement as an active agent is necessary (bi’l-wujęb). If the moving body itself were the producer of movement, this relation would be necessary. But since contingency and necessity cannot coincide, the moving body has to be different for the principle or source of movement.

The Way Things are Set in Motion

There are two possible ways for a mover to set things in motion: It moves things either 1) Directly and by itself or 2) indirectly and by means of something else. A carpenter with his adz is an example for the second type of movement. The immediate act of the mover gives the notion of movement as a quality or property. On the other hand, the act of the mover by means of something else yields the notion of the moving body itself. The mover sets the subject of movement in motion without being in need of any intermediary agent like the attraction of the lover by the beloved or the movement of the one who has zeal and desire to learn by the learned one. This first mover, which itself does not move, either grants the moving body the immediate cause by which the thing moves, or it attracts the thing to itself as its final goal. Everything in the physical world brings about a certain effect not by accident or coincidence but through an extra power added to it from outside. And this ‘added quality’ is either the nature it has or the voluntary power it possesses. In both cases, this power should be related to the thing itself viz., it cannot be totally ‘relationless’ in respect to it. If this were a kind of movement brought about by the abstract or ‘remote’ agent (al-mufariq) in a universal manner, this would amount to something other than what is meant by movement in the usual sense of word. Therefore, the Prime Mover needs and, in fact, employs in things something by means of which it sets them motion. As Sadra will explain later in detail, this ‘something’ in all contingent beings is what he calls ‘nature’ (tabi‘ah).

The next problem Sadra tries to solve in this context is how the Prime Mover, which itself does not move, is related to contingent beings and material bodies. Sadra’s argument runs as follows: A thing’s being capable of receiving the effect of movement from the ‘detached’ agent (al-mufariq) may be due to three reasons: the thing itself, some special quality in that thing, or a quality in the detached agent. The first is impossible because, as shown previously, this would lead us to accepting movement-by-itself as a universal and intrinsic quality of thing ness. According to Sadra, the second option i.e., movement through a property or ability in the thing is the right view. The third option has some point to be explained. The actualization of movement through an aspect of the detached agent takes place when the detached agent originates an effect in the thing it sets in motion. This, in turn, may happen either through the will of the detached agent by manipulating something in the thing or through effecting it haphazardly according to its wish.

The last option is not tenable because it terminates the idea of order in nature. Chances or accidental coincidences (al-ittifaqiyyat) are not constant and continuous in nature

‘Chances, as you will learn, are neither constant nor dominant (in nature) whereas the order in nature is both dominant and continuous. There is nothing in nature that happens by chance or haphazardly. As you will learn, everything in nature is directed towards some universal purpose (aghrad kulliyah). Thus, the effect of movement cannot be brought about by chance. What remains, therefore, (as a valid option) is a particular quality in the thing (that moves). This essential quality (al-khassiyyah) is the source of movement, and this is nothing but potency (al-quwwah) and nature (al-tabi‘ah), by virtue of which things yearn, through movement, for their second perfection.’

Thus, we are left with the option that this effect occurs by means of an essential quality in the thing, which induces it to movement. This is what Sadra calls ‘potency’ and ‘nature’ (al-tabi‘ah).

After positing ‘nature’ as the immediate cause of all movement, Sadra opens a long parenthesis and delves into a discussion of how actuality precedes potentiality. This long discussion is meant to show that the very idea of contingency requires existential transformation and that the continuous renewal of contingent beings is an essential quality, which exists in concreto whenever possible beings are brought into actuality out of potentiality. Sadra’s arguments also reveal some interesting aspects of his theory of matter (maddah). Sadra substantiates his assertion as follows: Every created being is preceded by existence (wujęd) and matter (maddah) that bears it. This a quality inherent in all contingent beings. Otherwise they would belong to the category of either necessary or impossible beings. Matter with which the contingent beings are united acts as one of the immediate principles or causes of bringing contingent beings out of non-existence to actualization in the external world. In this sense, the subject of possibility or contingency (mawdu‘ al-imkan) has to be an originated entity (mubdi‘an), otherwise it would be preceded by another contingency and infinitum. Every possibility vanishes when it becomes something actual in the external world. This means that every contingency is preceded by another one until the chain of causation comes to an end in the Principle which has no contingency.

Here Sadra warns us by saying that the foregoing considerations may have conjured up the wrong idea that potentiality is prior to actuality. In fact, it is common tendency to think that potentiality is prior to actuality like a seed’s relation to a tree or like the theory of latency (kumun and buruz). Some have said that the universe was in disorder and God bestowed upon it the best of all orders. In the same manner, matter has been regarded prior to form, and genus to differentia.

According to another group of people whom Ibn Sina mentions in his al-Shifa’, hyle had an ‘existence’ before its form, and the active agent gave it the dress of the form. Some have held the view that all things in the universe were moving by their natural movement without any order. God arranged their movement and brought them out of disorder.

Sadra’s overall reply to these claims is that some cases, such as the relationship between sperm and man, potentiality precedes actuality in time. But, in the final analysis, potentiality cannot subsist by itself and needs a substratum to sustain it.

‘We say that, as far as the particular things in the world of corruption are concerned, the relation between (potentiality and actuality) is like the sperm and the human being. Here, the potentiality specific (to the sperm) has priority over actuality in time. But potentiality, in the final analysis, is preceded by actuality for a number of reasons. Potentiality (i.e., the potential being) cannot subsist by itself and needs a substance to sustain it. And this substance has to be something actual (bi’l-fi‘l) because whatever is not actual cannot exercise (any power) on something else. In the same manner, whatever is not existent in an absolute way cannot accept any (exercise of power). Furthermore, there are certain actual beings in existence that have never been and are by no means potential in essence such as the Sublime First (Principle) and the Active Intelligences (al-‘uqęl al-fa‘alah). Then, potentiality needs the act (fi‘l) (of realization) to bring it into actualization whereas this is not the case with what is actual. Potentiality needs another agent (mukhrij) to bring it (out of non-existence), and this chain undoubtedly comes to an end in an actual being (mawjud bi’l-fi‘l), which is not created (by something else) as we have explained in the chapter on the termination of causes…

The goodness (al-khayr) in things comes from the fact that they are actual whereas evil (al-sharr) stems from what is potential. A thing cannot be evil in every respect otherwise it would be non-existent. And every being, in so far as it is something existent, is not evil. It becomes evil as a privation of perfection such as ignorance, or it necessitates its own non-existence in other things such as injustice (al-zulm).

Since potentiality has some sort of actualization in the external world, its essence subsists by existence. And existence, as you have seen, is prior to essence in an absolute way. Therefore, potentiality as potentiality has external realization only in the mind. Thus, it is concluded that the actual is prior to the potential in terms of causation (bi’l-‘illiyyah), nature (bi’t-tab‘), perfection (bi’sh-sharaf), time and actual reality (bi’l-haqiqah).’

Nature as the Immediate Cause of Movement

As we have started previously, movement is the act of moving itself (mutaaarrikiyyat al-shay’) because it is continuous renewal and lapse. Then the immediate cause of movement should be something whose essence is not stable. Otherwise ‘a stable or enduring entity will contain in itself the passing phases of movement as a present fact, and this togetherness of all passing would amount to stability, not movement.’ This leads Sadra to the following conclusion: The immediate cause of every movement should be something whose quiddity (mahiyyah) is stable but whose existence (wujęd) is ever-changing.

‘The immediate cause of movement has to be something with a stable essence and continuously changing existence (thabitat al-mahiyyah mutajaddid al-wujęd). As you will see, the immediate cause of all kinds of movement is no other than nature (al-tabi‘ah). This nature is the substance by which things subsist and become actualized as a species (i.e., as a particular entity). This refers to the first perfection of natural things in so far as they are actual beings  (in the external world). Therefore it is concluded and established from this (consideration) that every physical being is a continuously changing entity with a flowing identity (sayyal al-huwiyyah) despite the fact that its quiddity is impervious to change.’

The statement that the subject of movement should be something with a stable essence is true only when we mean by ‘stable’ (thabit) the essence (mahiyyah), that is the mental image of things. Or, we understand from ‘stable’ the subject of movement, which is not a concomitant (lazim) for a thing’s actual existence. Thus, Sadra introduces here two kinds of movement. The first is the kind of movement, which every material substance possesses as a concomitant of its existential constitution. In other words, this kind of movement exists as an essential property of corporeal things. The second kind of movement, on the other hand, is that movement which occurs to things as an ‘accident’ as in the case of transposition, transformation or growth. Sadra calls the latter ‘movement in movement’ (harakah fi harakah).

Seen in this light, every moving body, in its fundamental constitution, possesses ‘nature’ that acts as the immediate cause of movement. This nature, however, is not something superadded to things from outside, like an accident, but conjoined inherently with substances. In this sense, nature is not only the immediate cause of natural movement (al-harakah al-tabi‘iyyah) but also that of forced or constrained (al-harakah al-qaysariyyah) movement. The immediate agent that causes movement employs nature to set things in motion.

‘And we are certain about the following conclusion on the basis of heart-knowledge (al-wijdan) rather than discursive proof (al-burhan): the cause that makes a thing yield and induces it to move from one place to another or from one state (of being) to another cannot but be an actual power inherent in that thing. This is called nature. Thus, the immediate cause of material movement (al-harakat al-jismiyyah) is the substantial power which subsists in things, and all the accidents are subservient to the sustaining form (al-surat al-muqawwimah), which is nature…

The philosophers have shown conclusively that every (physical body) which accepts the act of yielding (al-mayl) from outside has to have a natural inclination (mayl tabi) in itself. It is thus proved that the direct source of movement is something flowing with a continuously changing identity (mutajaddid al-huwiyyah). If this (substratum) were not to be something flowing and ever-changing, it would be impossible for these natural movements to emanate from the stable.’

In this paragraph, Sadra refers to Ibn Sina to support his thesis, and says that Ibn Sina has, in fact, accepted the principle that a stable being cannot be the cause of instability and permanent change. Ibn Sina, however, is to be corrected by saying that any kind of change and transformation that we observe in things externally goes back to the constantly changing structure of their substance. Every direct or indirect movement is ultimately connected to and an outcome of nature, namely the inner structure of things.

Nature as the Principle of Change and Permanence

After criticizing the philosophers’ idea of ‘two consecutive phases’ in movement, Sadra discusses briefly the problem of the connection of the changing to the unchanging and permanent principle. If every changing body is preceded by another changing body, this leads either to an endless chain or to a change in the First Principle, which is immune from change. Sadra eliminates this objection by saying that the renewal of material bodies is an essential attribute of things and not a quality added to them from outside. When a corporeal thing moves towards its ‘existential realization,’ viz., actualizes its potentialities by going through various forms and states of being, such as emerging from the potentiality to actuality or moving from one location to another, it possesses its immediate cause of movement in itself, and does not need an extra ‘cause.’ Even when an extraneous stimulator is required for a thing to move externally, this is made possible only by having recourse to the nature inherent in that thing.

Every natural body carries the principles of change and permanence in itself simultaneously. Nature, for example, remains as an enduring property in things while its very reality is change. In the same manner, there are certain things whose actuality is their potentiality such as the hyle, or whose plurality is their unity such as numbers, or whose unity is their plurality such as numbers, or whose unity is their plurality such as the material body with its components as a whole.

Thus, everything has a double-aspect in its essential constitution. In this respect nature and hyle appear to be the two basic points of connection between the changing and the unchanging.

Nature, considered in its aspect of permanence, is directly connected to the permanent principle; when considered in regard to its aspect of change and renewal, however, it is connected to the renewal of material bodies and the connection point between the potentiality and actuality of contingent beings. Taken in this sense, ‘these two substances (i.e., the nature and hyle) are simply means of origination and corruption of material bodies, and through them a relation is established between the eternal (al-qadim) and the created (al-hadith).’

The Category of Movement

The question of which categories of physical existence are capable of receiving change and movement is an essential one for Sadra because this is one of the points of divergence that marks off Sadra from the traditional philosophy of nature. Following Aristotle, Ibn Sina had accepted change in categories such a quality, quantity, and position but not the category of substance (jawhar). Since substance was regarded by Ibn Sina and his students as a stable substratum to which all accidental qualities are ultimately traceable, the acceptance of change in the substance of a thing would amount to the dissolution of that particular thing and there would be no subject for movement and change. For Sadra, however, since a stable substratum is not needed to support the ‘general existence’ of a physical body, change in the category of substance does not lead to the destruction of things. This is so because the subject of movement is ‘some subject’ (mawdu‘ ma) rather than a ‘particular subject’ (mawdu‘). Sadra’s analysis runs as follows:

When we say that movement is ‘within a category’ (maqulah) four possibilities immediately arise to consider: 1) the category is the subject of movement, 2) substance through a category is the subject of movement, 3) the category is a genus for movement and finally 4) the substance itself is changing gradually from one species to another or from one class to another.

Sadra emphatically rejects the first three possibilities by relying on his fundamental identification of the act of movement with the moving body. He repudiates the claim of the earlier philosophers that if we admit change in one of the four categories, then we would have to accept an infinite number of species being actualized in one single entity. The realization of an infinite number of species in a finite being is obviously impossible. In this respect, Sadra invokes Ibn Sina in support of his argument by quoting from his al-Ta‘liqat. What happens during the essential change of categories is not that at every successive moment, a new amount of quantity is added up to the thing, which maintains its previous existence quantity-wise.

Far from being added up to the thing in a cumulative manner, the infinite number of species exists only potentially for a thing due to the very definition of movement, i.e., that it is an intermediary stage between pure potentiality and pure actuality. During the process of movement, a physical body which goes through various degrees of existence ‘has a temporal particular quanta-entity which is continuous, gradual and in perfect proportion with the time instants of movement.’ Such a body does certainly have an infinite number of ‘instantaneous individuals’ (afrad aniyah) at every second. But these infinite instantaneous individuals exist only potentially and do not point to a real actualization in the extra-mental world. Blackness, for instance, has an existence in actuality and this existence is of such a nature that the mind can abstract from it a series of new species at every instance. This particular existence of blackness is ‘stronger’ than ‘instantaneous existences’ (i.e. the possible species abstracted by the mind) in that as an actual existent, it represents (misdaqan) in itself many species. By the same token, animal’s existence is stronger than a plant’s existence simply because, as a single unity, it contains and represents every shade of existence that the plant possesses. The same holds true for the intensification of blackness since it encapsulates whatever blackness exists in the ‘weak black entities.’ Thus, movement in categories, which brings them at every successive instant from one species to another or from one class to another, is conceived as a plausible and, in fact, the only possible process.

As for the category’s being a species for movement, this is not tenable because, as Sadra has repeatedly stated, ‘movement is not the changed and renewed thing but the change and renewal itself just like immobility is not the immobile ting but the immobility of a thing.’ In this regard, it should be emphasized that the establishment of movement for the constantly renewing body is not like the occurrence of an accident to a ‘self-subsisting subject’ (al-mawdę’ al-mutaqawwim bi-nafsihi). The idea of such a stable subject is rather one of the ‘mental accidents’ (al-‘awarid al-tahliliyyah) i.e. mentally abstracted and posited accidents that the mind constructs. This underlines the intrinsic relation between existential movement and actually existing entities, and indicates that the ‘separation’ of substantial movement from corporeal things is nothing but an outcome of the mind’s analytical activity. The ‘occurrence’ (‘uręd) of movement to things is an event that takes place only at the level of conceptual analysis viz., when the mind analyzes an actually existing entity into its constituent parts. As Sabzawari states in his note, the distinction is merely a matter of ‘naming’ (bi-hasab al-‘unwan). At best, the attribution of mental accidents to subject can be compared only to the attribution of differentia to genus.

Sadra sums up his discussion by saving that ‘the meaning of movement being in a category is that the subject (i.e., the substance) is bound to change gradually, and not suddenly, from one species to another or from one class (of being) to another. 

The Question of Quantitative Change

Although the Peripatetic philosophers had affirmed, with Aristotle, that all categories, with the exception of the category of substance, undergo change, the explanation of quantitative change had posed some difficulties for many of them. As Sadra notes, Suhrawardi and his followers had even denied quantitative change completely. The main difficulty seems to result from the assumption that increase and decrease in quantity necessitates the replacement of the original quantity as well as that, which is quantified, i.e. the physical body that undergoes quantitative change. In contrast to the idea of quantitative change as rupture and replacement, Sadra sees change in quantity as a continuous and single process. Sadra’s detailed discussion can be recounted as follows:

Since movement, as we have noted before, signifies the actualization of certain qualities and quantities that exist for physical bodies potentially, Sadra says that to become black is, in fact, not the increase of blackness but the increase of the subject in blackness. It is not the case that in the process of increasing there exist two blacknesses, the original blackness and the newly emergent one. The mind conceives this process as the conjoining of two separate and discrete quantities of blackness. In the order of existence, however, blackness has only ‘one single continuous identity (huwiyyat shahksiyyah wahidah) evolving in perfection at every instant.’

When we say that blackness, in its upward movement towards higher degrees of perfection, has only ‘one single continuous identity’ (huwiyyah wahidah ittisaliyyah), we admit some kind of ‘hierarchy of intensification’ (maratib al-ishtihad). In this case, says Sadra, three points should be made clear. Firstly, as we have stated previously there is an infinite number of species in one single entity only in potentia. In the order of existence, this fact is complemented by the principle that ‘one single continuum has only one single being’ (al-muttasil al-wahid lahu wujęd wahid). Secondly, although blackness has one single continuous identity in its perfection or imperfection, ‘various species, essential properties and logical differentiae’ occur to it in regard to its existential renewal. According to Sadra, such a transformation in the substance of a thing is quite possible because it is existence that is fundamentally real and principal, essence being thereby subject to it. Thirdly, the frozen picture of the increasing entity presents to the mind some ‘instant-points that have occurred actually and some instant-points that may occur potentially. But, as Sadra repeatedly states, it is the mental representation of the order or existence that yields the idea of quantitative change as a succession and conjoining of two discrete species or entities. In contrast to the atomistic picture of the physical world, the corporeal body that undergoes quantitative change always maintains its identity as a single and unbroken unity. Thus, an entity of such a nature is ‘ a new emergent every moment with a continuous body in respect of which if we say it is one, we would be right or if we say it is many, … enduring or changing, all these would be right.

If we say that it persists identically from the very beginning of change to the end, we shall be speaking the truth; if we say every moment it is a few emergent (hadith kulla hin) this will be equally true.’

In order to further emphasize movement as a continuous process, Sadra turns to Ibn Sina one more time and takes him to ask on the question of movement in the category of substance. Ibn Sina had conceived movement in substance not as a single continuum but rather as the destruction of the original substance and its replacement by another one. In other words, Ibn Sina’s criticism was based on the assumption that is substance were capable of intensification and diminution, the species that determines and particularizes it would either remain the same or change into another species. In either case, we would have to accept that there has been no change in the substance, or that the original substance has been destroyed.

Against this criticism, Sadra comes up with the following answer, which summarizes also his doctrine of the gradual perfection of existence in terms of plurality-in-unity and unity-in-process.

‘If in the statement: ‘either its species persists during intensification’ by ‘persistence of species’ is meant its existence then we choose that it does persist because existence as a gradually unfolding process has a unity, and its intensification means its progressive perfection. But if the question is whether the same specific essence which could be abstracted (by the mind) from it previously still continues to exist – then we choose to say that it does not remain any longer. But from this, it does not follow that an entirely new substance, i.e., existence has arisen; it only means that a new essential characteristic (or specific form) has been acquired by it (i.e., by existence…). That is to say, this substance either has been perfected or has retrogressed (the latter however does not actually happen) in the two modes of existence and hence its essential characteristics have been transmuted. This does not mean that an actual infinity of species has arisen (just it did not mean in the case of black that an actual infinity of black colors had arisen); it only means that there is a single continuous individual existence characterized by a potential infinity of middle points in accordance with the supposed time-instants in the duration of its (moving) existence… There is no difference between the qualitative intensification called ‘change’ and the quantitative intensification called ‘growth’ (on the one hand), and the substantive intensification called ‘emergence (takawwun)’ (on the other) in that each one of them is a gradual perfection, i.e., a movement towards the actuality of (a new) mode of existence.’

The gist of the foregoing argument is that existence, as an unfolding single unity (al-wujęd al-muttasil al-tadriji), travels through various essences, and assumes different forms and modifications at every moment. The gradual passing of the substance reaches a higher and more perfect mode of being. This continuous process, however, does not split it into different and discrete units.

The Identity and Endurance of Physical Bodies

In order to account for the substratum that endures throughout the entire process of change, Sadra states that some matter (maddatęn ma) particularized through a form, quality or quantity is enough for substantial change. Put differently, during the process of the gradual perfection of a substance, a certain amount of matter (existence) remains as the persisting principle while assuming the becoming united with various forms, qualities, quantities and positions. This is very much obvious, says Sadra, in the attribution of form to one single material body. But this point i.e., the persistence of a certain amount of matter (existence) with its variegated modifications and particularizations is so subtle that the previous philosophers, including Ibn Sina, have acknowledged that the mind is hardly capable of perceiving it in its entirety. After stating this historical point, Sadra sets out to establish this peculiar relationship between form and matter as an essential property of physical bodies.

According to Sadra, the problem of quantitative change that has led many, including Suhrawardi and Ibn Sina, to the denial of change in the category of substance can be resolved by having recourse to the following precept: What is required in the process of movement is not a definite quantity but ‘some quantity’ (miqdar ma) by which a thing or matter becomes particularized. Suhrawardi’s problem had arisen out of the assumption that ‘the addition of a certain amount of quantity to another (block of) quantity (i.e., the increase or decrease of a certain quantity) necessitates the destruction of the original quantity and when a part of this quantity is taken away from the whole this also necessitates the destruction (of that which is quantified).’

According to this point of view, any quantitative change in the direction of increase or decrease leads to the destruction of the body itself. Ibn Sina had faced a similar difficulty in explaining change in organic bodies. In fact, Ibn Sina ‘was not able to solve’ (ghayrah maqdęr ‘alayhi) the problem of identity in plants and animals because he had postulated that organic bodies, namely plants and animals, unlike man who has both the soul and the character, can posses no enduring quality.

In response to these difficulties, Sadra asserts that ‘the subject of movement is a particular entity (al-jism al-mutashakhkhis), not a definite quantity (al-miqdar al-mutashakhkhis). And the particularization of a thing requires a definite quantity for the thing in its movement from one place to another as the physicians (al-atibba’) have asserted in regard to personal character (al-mizaj al-shakhsi). The movement takes place in the particularizations and (various) stages of quantities. Therefore, what is enduring (at this point) from the beginning to the end of movement is different from what is changing. The disjunction (al-fasl) and conjunction (al-wasl) (of definite quantity with matter) do not cancel each other out except in the case of conjoined quantity taken, as a mental abstraction, in its natural state, i.e., without being united with matter.’

As this quote shows, the substratum of quantitative change is not definite quantity but matter with some quantity. Therefore, the destruction of definite quantity does not necessitate the destruction of the thing itself. ‘The natural body’ (al-jism al-tabi‘i) which is composed of thingness and form also preserves its species by dint of the definite form (al-surat al-mu‘ayyanah) which is the principle of its final differentia (al-fasl al-akhir).’ Thus it is concluded that no kind of qualitative or quantitative change leads to the destruction of a thing as long as the definite form endures.

Change and Identity in Physical Bodies

After securing the existence of physical bodies when they undergo substantial change, Sadra proceeds to the most important and intricate part of his theory of substantial movement, namely the preservation of the identity of a changing body. Reference was already made to the idea that the differentia by its very definition ensures the endurance of some quality or quantity-in-general despite the fact that the definite quality in the changing body is destroyed at every successive phase of movement. Sadra states that whatever has the final differentia as its principle of perfection has some sort of preservation-in-general. The redefinition of differentia as a thing’s principle of perfection becomes a forceful argument for Sadra because he casts the whole story not within the framework of traditional genus-differentia account but of his ontology. At this point, the differentia is transformed from being a mere principal of difference (al-ikhtilaf) among genuses into the principle of existential individualization of particular entities. As a novel contribution, Sadra equates differentia, viz. the principle entities. As a novel contribution, Sadra equates differentia, viz. the principle of diversity and unity with existence (wujęd). Sadra illustrates this point as follows:

‘Being capable of growth (al-nami) is the plant’s differentia whereby its being is perfected, since its perfection is not due to its being a body alone. Rather, it (i.e., ‘being capable of growth’) is its principle of potency and carrier of its potentiality. Hence, there is no doubt that the change of bodily entities does not necessitate change in the substantial being of the plant itself since body is regarded here only in a general manner (‘alawajh al-‘umęm wa’l-itlaq), (i.e., as body-in-general), not in a specified and determined manner (‘ala wajh al-khususiyyah wa’l-taqyid) (i.e., not as body in-particular or as a particular body). The same holds true for the animal which is constituted by being capable of growth and perception, and for every being whose existence is constituted by matter and form such as man in relation to his soul and body. Hence when ‘being capable of growth’ changes in quantity, its ‘thingness’ (jismiyyatahu) as an individual entity remains the same. Thus it (the plant), insofar as it is a natural body-in-general is destroyed as an individual entity, but insofar as it is a natural body capable of growth, is not destroyed, neither itself nor even its part. Because every being part of which is nothing but body-in-general in an individual (entity) is established (in the external world) in a manner of continuous existence (al-ittisal al-węjędi). On the basis of this principle, the endurance of an animal together with its substance of perception can be explained. In the same manner, man in his old age loses most of his power of vegetation whereas his identity remains the same.’

According to Sadra, the above description of qualitative and quantitative change goes true for all the natural bodies that have a constantly changing existence with a perduring identity. In every change and movement, there remains an original principle, which is perpetuated and perfected by the final differentia. For example, the final differentia in composite beings comprises every successive phase of increasing perfection, which the intensifying or moving body goes through. Therefore, the succession of various degrees of being that lead a thing to a higher state of being is not something added to a thing’s final differentia from outside. As we have stated before, a simple being (basit al-haqiqah) contains in itself lower levels of being, and this principle is employed here by Sadra extensively to explain the peculiar relationship among species, genuses and differentia. Within this framework, every species comprises in its very structure whatever is possessed and shared by lower species. Also important is the fact that the species is perfected into a genus by differentia. The most crucial point, however, is that Sadra takes differentia not simply as a mental notion abstracted from physical entities as the principle of diversity but equates it with existence, which functions, as we have seen, as both the principle of unity and diversity.

The existential relationship between a thing and its essential properties, namely what Sadra calls ‘concomitants’ (lawazim), can also be explained by having recourse to the definition and description of things in our ordinary language. When we want to define or describe something, we naturally refer to its essence as well as its essential properties that are included in its definition. Sadra calls such properties ‘a mode of being’ (nahw al-wujęd). Thus, in every mode of being, a particular piece of concrete reality appropriates and displays certain qualities that yield its ‘derived differentia’ (al-fasl al-ishtiqaqi). These distinctive qualities are generally called the ‘essential properties of a thing’ (al-mushakhkhasat). They constitute what Sadra calls the ‘signs of particularization’ (‘alamat li’l-tashakhkhus).

‘The (word) sign here refers to the name of a thing by which its concept is expressed. In the same manner, the derived real differentia (al-fasl al-haqiqi al-ishtiqaqi) is described as logical differentia (al-fasl al-mantiqi) in the case of ‘being capable of growth’ for plants, the sense perception for animals, and reasoning for human beings. The first of these (descriptions) is a name for rational soul. These are all derived differentia. The same holds true for all the other differentia with regard to the composite substances (al-murakkabat al-jawhariyyah). Each of these (bodies) is a simple substance designated by a universal logical differentia (fasl mantiqi kulli) as a matter of naming things (tasmiyat al-shay’). But these substances are in fact simple and specific (i.e., particularized) existences with no essence.

In the same manner, the concomitants of individual entities are assigned to their individual possessors through naming. Thus, particularization is a mode of being. A particular entity becomes particularized by itself and these concomitant (properties) issue forth from it just like the emanation of a ray of light from it source and of heat from fire.’

The logical differentia as a universal refers to the place of entities in the conceptual order whereas the real or existential differentia refers to their individuation and particularization (al-tashakhkhus) in the existential order. At the conceptual level, we distinguish between a thing and its existential properties and thus obtain the essence-existence bifurcation. We apply this conceptual process only ‘to name a thing’. In reality, however, there are only individuated concrete existents, simple and unique, without requiring any ‘quiddity.’ Thus, the particularization of a thing comes about by its assuming a mode of being with certain essential properties (al-mushakhkhasat). In other words, the relation between a thing and its existential properties is reversed:

The thing does not become particularized because of having such essential properties, but on the contrary, these properties come into being as a result of thing’s particularization in the existential order just like the expansion of a beam of light from its original source of light.

The following conclusions can be derived from Sadra’s argument. First of all, substance (jawhar) changes in accordance with the change of its essential properties. With this, the dividing line between substance and accidence becomes, in Sadra, rather provisional. Therefore, a material substance is essentially ‘a substance that is by itself continuous, quantified, positional, temporal, and inhering in a definite place. The change of quantities, colors and positions of the substance necessitates the renewal of the definite quantity of the individuated material substance.’

Thus, we arrive at a twofold picture of the natural world in which the ‘material substances’ or ‘bodily natures’ are aptly regarded as the proper locus of two interrelated aspects: the aspect of transciency and the aspect of perpetuity.

‘There is no doubt that every material substance has a continuously changing nature on the one hand, and an enduring and unchanging structure on the other. The relation between the two aspects is similar to the relation between the body and the soul. While the body is in constant change and flow, the human soul endures because it preserves its identity by the passing of essential forms (al-amthal) in an uninterrupted continuous process (wurud al-amthal ‘ala’l-ittisal).’

The nature forms of material substances share the same characteristics. They are renewed every instant as far as their material, positional, and temporal existence is concerned, and there is a gradual and steady origination for them. As far as their mental existence and abstract Platonic forms are concerned, however, they are eternal and perpetual in the knowledge of God.’

Thus, Sadra locates the enduring mental forms of the natural substances within the unchanging realm of Divine knowledge. With this, in a sense, the ‘great chain of being’ that Sadra has been expounding according to his theory of substantial movement comes to a full circle.

Concluding Remarks

Sadra’s highly complex and original theory of nature yields a number of important results. First of all, Sadra does away with Aristotelian notion of a solid substratum as the basis of change and renewal in the world of nature. Instead, he resolves the realm of physical bodies into a ‘process of change’ by introducing the notion of change-in-substance. Construed as such, the world of nature becomes a play of contingencies while preserving its ‘substantial’ unity and integrity. Anticipating the quantum view of the physical world, Sadra offers a new interpretation of the world of nature without necessarily upholding any solid or gross material substratum as the basis of physical entities.

Being aware of its central place in his thought, Sadra makes a profuse use of his notion of substantial movement and applies it to a number of philosophical problems. The relation between the changing (al-mutaghayyir) and the permanent (al-thabit), i.e., God and the world of creation; origination of the soul form the body, i.e., the Sadrean doctrine that the ‘soul is bodily in its origination and spiritual in its survival’ (jismaniyyat al-hudęth ruhaniyyat al-baqa’), or the rejection of the transmigration of souls (tanasuhk) are only a few among the philosophical problems that Sadra addresses on the basis of his concept of nature and movement-in-substance.

With this grand-scale application, Sadra’s natural philosophy is assigned a more central role in the analysis of metaphysical problems, and one important consequence of this is the narrowing down of the gap between the physical and the metaphysical. Thus, Sadra moves easily between physical realm and metaphysical concepts with great lucidity, and makes a number of revisions in both fields. In a sense, the interdependence between the physical and the metaphysical is made explicit without subverting the one to the other. It is true that Sadra’s natural philosophy is based on ‘metaphysical vision’ and not on experiment. This, however, does not seem to take away ay value from his philosophy. In fact, this may be seen as a case of ‘philosophical intuition’ in the sciences the peak example of which we have seen in the field of physics, at the beginning of this century, in the work of Einstein. 




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