Descartes and Gassendi

A substance is the Prius of a Cartesian theory of knowledge. In the preface to his Principles of Philosophy (AT IXB) Descartes says that in order for our knowledge to be perfect we must start from first causes or principles. These principles must satisfy two conditions: (i) they must be so clear and evident that the human mind cannot doubt them when it fixes its attention to them (Most of Descartes Rules for the direction of the mind is concerned with the question – how to fix one’s inner gaze to the Ideas we have within. Descartes’s method is concerned with the ability to draw attention inward to extract principles of knowledge that are clear and evident and compel assent on immediate perception), (ii) knowledge of every other thing must depend on the principle such that the principle can be known without the knowledge of these other things but not vica versa (Hence a substance is that which can be conceived without modes but not vica-versa). The knowledge of these other things must be capable of being deduced in clear and simple steps from the original principle just as from the definition of a triangle we can deduce the Pythagorean Theorem.

The problem is what if the same attribute belongs to more than one substance. In that case they cannot be deduced from the substance for deduction is a necessary relation and thus an attribute that only contingently belongs to a substance cannot be deduced from its nature. Here we see that Descartes radically re-conceptualizes what a concept of a substance. This is done by first (i) identifying substance and essence and (ii) conceiving the relation between essence and modes as a causal relation and (iii) conceiving the causal relation as a necessary one thereby ruling out causal interaction and the possibility of the same effect having different causes.

 

(I) Substance = Principal Attribute (Essence): In Principles of Philosophy 1.53 Descartes defines a Principal Attribute:

“Each substance has one principal property that constitutes its nature and essence, and to which all its other properties are referred. Thus extension in length, breadth, and depth constitutes the nature of corporeal substance; and thought constitutes the nature of thinking substance.”

 

In the fourth replies Descartes says:

 

“We do not grasp substances immediately, as I have noted elsewhere, but only as a result of perceiving certain forms or attributes, which must inhere in something (res) in order to exist. That thing in which they inhere is what we call substance. If we subsequently wanted to strip that same substance of those attributes by which we grasp it, we would be destroying our entire knowledge of it. We could pronounce some words about it, but we would not clearly and distinctly perceive their meaning.”

 

In Principles 1.62 Descartes says that there is only a distinction of reason between substance and essence. We have a distinction of reason when the same substance is cognized by two different concepts. The thoughts through which we grasp the same entity differ in having different concepts or predicates but ontologically the entity referred to by both is the same. For example there is only a distinction of reason between mountain and a valley. A confusion arises because Descartes says that a distinction of reason is founded in reality but Pasnau (2011) explains what this means:

 

“Although there was controversy among scholastic authors over the subtleties of the conceptual distinction, it was a bedrock principle that where there is only a conceptual distinction between x and y, then x = y. The very point of speaking of a conceptual distinction—a distinction of reason—is to stress that the only true distinctness occurs on the side of our concepts. For Descartes to deviate from this usage would amount to a gross and embarrassing misuse of one of the basic philosophical concepts of his era….For when he insists that even a conceptual distinction has a foundation in reality he is appealing to a standard distinction between a conceptual distinction motivated by some feature of reality, and one where reason does all the work, without any encouragement from reality. An example of the first kind would be the distinction between God’s goodness and wisdom, which has a foundation in the created world inasmuch as some things reflect God’s goodness, and others reflect God’s wisdom. An example of the second would be to think of a thing as identical to itself. Descartes says he recognizes only the first sort of conceptual distinction; even such cases, however, involve no distinctness within the thing itself. Thus a conceptual distinction within God can be grounded in reality, but cannot be grounded in God, who is perfectly simple. Although Descartes does not explain things to this extent, he uses the right sorts of examples. He speaks, for instance, of God’s justice and mercy as conceptually distinct.”

 

Further Descartes tells us that there is only a distinction of reason between a substance and its existence, duration and number. The substance is an existing essence and is particular in nature. Thus Descartes is a nominalist. The notion becomes clear in a response Descartes made to Arnauld’s query. Arnauld had asked how thought can be the essence of the mind. Since thought is a particular mode of the substance to say that thought is the essence of the substance would imply that the essence keeps changing. If on the other hand a thought is a universal then it would be a product of intellectual abstraction and not something real. Descartes responded to this:

 

“Just as extension, which constitutes the nature of body, differs greatly from the various shapes or modes of extension that it assumes, so thought, or a thinking nature, which I take to constitute the essence of the human mind, is very different from any particular act of thinking. It depends on the mind itself whether it produces these acts of thinking or other ones, but not that it is a thinking thing, just as it depends on a flame itself, as an efficient cause, whether it extends in one direction or another, but not that it is an extended thing. So by ‘thought’ I do not mean some universal that covers all modes of thinking, but a particular nature that receives all those modes, just as extension is a nature that receives all shapes.”

 

Now an essence is a property such that a substance can lose it only by being destroyed. Hence a substance has its essence necessarily and thus no two substances can share the same essence for then they would be identical. Descartes says that two substances are distinct if one can exist without the other (Second Replies) and since a substance cannot exist without its essence it is not possible that two substances can both be different and yet share the same essence. Again it should be emphasized that this position amounts to a nominalism.

 

(II) Essence and Its Modes and Cause-Effect Relation: It was mentioned above that a determinate property necessarily presupposes a determinable property. This is because the determinate property is necessarily contained in the determinable property (I have borrowed the determinate – determinable terminology from Secada’s Cartesian Metaphysics – 2000). Every property a substance can have is either its principal attribute or a determinate property necessarily referring back to its principal attribute which is a determinable property but never a determinate property. The purpose of analysis from compound properties to simple properties is thus to achieve a clear and distinct perception of a property as being a necessary consequence of the essence of a substance. Since nothingness has no properties; everything that exists is either a substance or a property / attribute / mode (I am using these words interchangeably) of a substance. From the following line of argument we can deduce that a substance has all its properties essentially:

 

(i)              A substance has only one essence

 

This follows from the fact that there is only one substance, everything is identical with itself and there is only a distinction of reason between a substance and its essence. So if substance is a particular so is an essence.

 

(ii)            A substance has its essence necessarily or essentially

 

Because identity is a necessary relation.

 

(iii)          No two distinct substances can have the same essence

 

Corollary of (i) and (ii)

 

(iv)          Any property not identical with the essence is a determinate property of its essence

(v)            Essence is the highest-order determinable property and is never a determinate property

(vi)          No two distinct substances can share any property whatsoever

 

Two substances could share a property only if the property would not necessarily refer back to its essence and no since no two substances can have the same essence; no two substances can share the same property. The relation between substance and essence on one hand and essence and modes on the other is thus conceived to be a necessary relation. (This discussion is indebted to Secada 2000)

 

According to the axioms given by Descartes in his Second Replies we have the following:

 

(i)              Nothing cannot be the cause of anything

(ii)            Whatever reality or perfection we find in the effect must have been contained formally and eminently in its first adequate cause

 

Otherwise there would be present some property in the effect that would be caused by nothing violating the first axiom.

 

The formal and eminent clause will be revisited in the next section but here we may note a triangle has as its cause a figure formally but extension eminently (extension is not a figure because extension is not itself extended). The formal cause is the immediate cause presupposed by a property and the eminent cause if the highest kind of cause. To explain something we need to trace it back to its highest eminent cause. From this it should be clear that the causal relation is the reduced to the essence – modes relation and is thereby a necessary relation.

 

(III) Just as no two distinct substances can share the same essence and its determinate properties no two effects can have the same cause. Thereby causal interaction between distinct substances is ruled out.

Ultimately in the Cartesian System only God has any real causal efficacy because he is Causa Sui (Self-Caused) whereas other substances are contingent existents and thus require the concurrence of God to exist. God is both the Principle of knowledge and the Principle of Being in the Cartesian System unlike in the Scholastic Tradition where God was the Principle of Being but not the Principle of Knowledge. But even though God is the Principle of Knowledge Descartes does not begin with God because if he was giving a synthesis or demonstration we would begin with God. Rather he intends to give an analysis – to show how he reaches certain knowledge about God and the ‘order of reasons’ whereby each step is justified or shows how and why that discovery was made and does not presuppose steps that come after. The point is acquisition of new knowledge rather than presumption that we know from the beginning. 

Descartes uses the method of exclusion to arrive at a clear and distinct Idea. Let us one by one exclude all properties that soul possesses and note the consequences of excluding those properties from the soul. If there is a property which if excluded from the soul would lead to annihilation of the soul i.e. something without which soul cannot presumably exist then that property must be regarded as specifying the essence of the soul. Now I can deny the body and everything belonging to the body from myself but not thought hence the latter is the sole candidate for the essence of the soul. The method of exclusion allows us to distinguish an Idea from every other and thus to acquire a simple and clear Idea of ourselves.

Arnauld raised an objection to this: we can conceive of a right triangle without conceiving that the Pythagorean property belongs to it; likewise we can conceive that we can exist without the body without the nature of mind excluding the body. To this Descartes’s response is disappointing even though Arnauld was content with it. He says: “there is no way in which the triangle can be distinctly understood if the ratio which obtains between the squares on the hypotenuse and the squares on the other sides is said not to hold.” The point is I cannot be said to have a complete Idea of something if the exclusion of some property from it is responsible for the Idea being incomplete. Georges Dicker endorses this move thus:

 

“There is something to be said for the idea that while one can have a clear and distinct conception of X without being aware of all the properties that follow from one’s conception of X, one fails to have a clear and distinct conception of X if one conceives it not to have a property that follows from one’s conception of X. Furthermore, it will not do to object that for all Descartes knows, perhaps

“I am extended” does follow from his conception of himself; for Descartes’s careful examination of his idea of himself in Meditation II seems to show that this is not the case (whereas a careful examination of his conception of a right triangle would show that the Pythagorean property does follow from that conception).” (Dicker 2012)

 

To have a complete Idea we need to be aware of all the properties that flow from our conception of its substance. If any one of these properties is denied of something X then we cannot be said to a clear Idea of X. Dicker thinks that we can conceive say a right triangle without conceiving the Pythagorean property to belong to it. But we cannot have a clear Idea by excluding the Pythagorean property. A Complete or a Clear Idea would require we include that property in our conception. But in order to do that we need to know that - that property can be said to belong to the right triangle. Now let us come back to Soul and Extension. The exclusion of extension from soul has to be such that I can be certain that extension does not belong to the nature of the mind – my exclusion should track the separation of two different substances. How to be sure of this? Descartes reply in effect is that I can have a complete or clear Idea of myself while excluding extension and this suffices to demonstrate their difference. But this begs the question. Why should a materialist for instance agree that Descartes has a clear Idea of his soul whilst he is excluding matter – shouldn’t matter be included for us to have a clear Idea of the soul? Descartes cannot reply that his conception of the soul does not reveal extension to be a part of it. For the materialist could equally urge that therefore we cannot be said to have a complete Idea of the nature of the soul. As Gassendi points out from “I do not know I am dependent on the Body” we cannot infer “Mind is independent of the Body”, because unknown to me the nature of the soul might be such that it does not exclude matter from it. Thus also the inference from ‘I can think’ to ‘I am a thinking thing only’ is invalid.

 

The problem is the nature of exclusion has to be complete and mere conceivability of absence of exclusion in the conception of the soul does not make the conception complete. Descartes implicitly recognized this problem in his 1644 letter to Mesland. He distinguished between abstraction and exclusion. I know by abstraction the Idea of soul “does not represent to me as dependent on the body and as identified with it” but this does not suffice to prove that soul is distinct from the body. But I know by exclusion that the Idea of the soul “represents it to me as a substance that can exist even though everything bodily be excluded from it.”

 

The problem is in order to have a clear Idea of the soul I need to exclude ‘everything bodily from it’ and that is not possible till a) I have a clear and complete Idea of Matter or b) I have a clear Idea of the soul. If I had a clear Idea of the soul then I wouldn’t need to exclude everything material from it; the clear Idea alone should have sufficed to tell me that thought is the essence of the soul. But the fact that I need to consult the Idea of Matter to arrive at the essence of the Soul indicates I do not have a clear Idea of the soul. This is in essence Malebranche’s argument against Descartes. To have a clear Idea is to know what possible modifications a substance can take. Can matter be a modification of the soul? For any mode of a substance if I cannot tell whether it does or does not belong to a substance then I do not have a clear Idea of the substance. Since we cannot arrive at the essence of the soul without excluding matter from it and we cannot exclude matter merely by consulting the Idea of the soul we cannot be said to have a clear Idea of the soul.

 

The point can also be made thus: Can Descartes assert what we can dub the Transparency Principle (to borrow Pasnau’s terminology (2011)):

 

“….. Nothing can be in me of which I am entirely unaware.” (First Replies).

 

He cannot assert this principle until he shows that (a) thought is the essence of the soul (b) And to show that he has to exclude matter from the soul (c) But to exclude matter it is not enough to say that I have a clear Idea of a soul that tells me that nothing material exists in it for this would lead us back to (a) making this an instance of circular reasoning. 

 

To elaborate, consider the question - Is it possible that soul is a substratum of both consciousness and matter? Descartes argues that our Idea of Soul tells us that soul can exist even if matter were eliminated from it but it couldn’t exist if thought were eliminated from it. The problem here is that our elimination process informs us that there is an absence of knowledge of matter within us – it does not however give us knowledge of absence of matter in us. There is no contradiction involved in thinking that the soul is extended and thus no reason to believe that the soul cannot be both extended and conscious. Thus there is no way Descartes can rule out this possibility. ‘A careful examination’ of the soul would not suffice until it is assumed that the nature of the soul is transparent which depends on its essence being of the nature of consciousness – which is really what Descartes has set out to prove. 

Can we trace the problem further down in the very conception of substance in the Cartesian system? Since substance is the prius of knowledge in the Cartesian system if concept of substance itself is unintelligible then that would have a negative impact within the whole system. This is what Gassendi attempts to show.

Gassendi’s Objection:

“When you go on to say that you are a thinking thing, we know what you are saying; but we knew it already, and it was not what we were asking you to tell us. For who doubts that you are thinking? What we are unclear about, what we are looking for, is that inner substance of yours whose distinctive property is thought.”

 

This argument is a challenge to the Transparency Principle. To this Descartes replied that:

“I have never thought that anything more is required to reveal a substance than its various attributes; thus the more attributes of a given substance we know, the more perfectly we understand its nature”

 

Gassendi’s counter-reply makes an interesting point:

 

“…… an attribute or property is one thing, and the substance or nature to which it belongs or from which it flows another. So to grasp the attribute or property, as well as the aggregate of properties, is not thereby to grasp the substance or nature”

 

The problem arises when as we have seen Descartes draws a distinction between a substance and its attributes in the Wax Argument. Because the two are distinct – senses which grasp the sensible qualities of a substance do not therefore grasp the substance itself because a substance is something that remains invariable through change and is a particular nature capable of receiving an infinite number of modes. Descartes however does not accept that we can grasp a substance in itself apart from all its attributes. A substance is always grasped through one or other of its attributes (Principles 1.52). Does this involve a contradiction? Is it possible that through God’s concurrence a substance can exist without attributes (i.e. a pure substance) or does it always exist with atleast one attribute? Gueroult (1984) believes there is no problem either way because since thought is the essence of the thinking substance (for instance) we can also take thought to be both the essence and a mode of the substance at the same time. Pasnau (2011) however finds this puzzling because in the Cartesian Ontology substance and modes both are real and yet necessarily tied to each other. Even though there is only a distinction of reason between substance and essence, the relation between the substance / principal attributes and its modes is not of identity as pointed out. This agrees with what Descartes says – modes depend for their existence on the substance but not vica-versa. This way he draws a modal distinction between substance and its attributes as opposed to a real distinction between one substance and another. But Pasnau says that this implies a metaphysical composition – two parts one a substance and another a mode joined together. Without the modes the substance is nothing but a pure potentiality or power to modify or be modified in a certain way. He finds this notion analogous to the notion of a prime matter in scholastic theory – a theory repudiated by Descartes for its obscurity. Yet Descartes too is indulging in the same obscurity by countenancing a substance which is nothing but a pure potentiality.

Gassendi’s objection had repercussions within the Cartesian system. Malebranche denied we know the essence of the soul. We know the existence of the soul through inner sentiment or an inner sensation but just as a sensation is incapable of revealing to us the nature of the external object that caused it within us, similarly it does not inform us about the nature of the inner substance. However it is a reliable guide as far as the question of existence of the soul is concerned. Malebranche further points out that if we really knew the essence of the soul then we would know that colours etc. do not belong to external objects but are rather modifications of the soul. Even though we may not be able to deduce every mode a substance can have from the knowledge of the nature of the substance; for every mode we should be able to tell to which substance it belongs. Otherwise we do not have a clear and distinct idea of a substance. Clearly we lack this knowledge and even when through analysis (involving comparison with the idea of extension) we can trace back colour to belong to the essence of the soul it is debatable that we see clearly how colour could be a mode of the thinking substance – no one takes soul to be coloured. Malebranche believes that there is an Idea of the soul but it is hidden from us by God. If we really knew the essence of the soul we would know how and why it is capable of modifying itself into various modes but we lack this knowledge as the case of colour shows. Even if this objection is successful the rationalist paradigm can still be salvaged.