Leibniz's Theory of Knowledge

 

Leibniz’s conception of substance differs in important ways from Descartes and Spinoza. A substance in Leibniz’s philosophy is a monad and its characteristic mark is unity:

 

“It is worth investigating in what way a being through aggregation, such as an army or even a disorganized multitude of men, is one; and in what way its unity and reality differ from the unity and reality of a man. . . . The chief point is this: an army accurately considered is not the same thing even for a moment, for it has nothing real in itself that does not result from the reality of the parts from which it is aggregated; and since its entire nature consists in number, figure, appearance and similar things, when these change it is not the same thing, but the human soul has its own special reality so that it cannot come to an end by any change in the parts of the body.” (Letter to Arnauld)

 

An aggregate always presupposes a unity because an aggregate is nothing but a collection of simple things (Monadology 2) and non-derivative unity can belong only to that which is simple or without parts. These simple entities can be nothing else but monads. If they are taken to be atoms in the way conceived by Epicurus possessing extension then since anything that possesses extension is infinitely divisible it cannot be said to possess the true unity out of which compound entities can be composed. Neither can these atoms be like mathematical points completely lacking in extension because if they themselves lack extension then they cannot compose extension and since extension presupposes continuity of a body it is evident that an extended body cannot be composed of mathematical points. Besides we cannot account for the presence of force in the world either on the atomic theory or in the Cartesian theory where matter is extension. Force cannot be deduced from extension. We have to look for a metaphysical cause for force within a substance or a monad.

 

The question of the relation between a whole and its part is a difficult one. If the existence of the whole is emphasized over the parts in the way Spinoza does then the parts have to be taken to be an abstraction and hence unreal. While countenancing the reality of parts over the whole would compromise the reality of the whole for it would cease to be a unity and become an abstraction from the parts. Hence we require a view where the relation between wholes and parts must be such that neither compromises the independence of parts nor does it destroy the unity of the whole. We will see how Leibniz sought to accomplish this goal through his monads and whether he was successful in his endeavour or not.

 

What is a substance? And what is its essence and what are its attributes? In a Letter to Foucher, Leibniz admitted that thought is not the essence of the soul:

 

“The author is right in saying that thought is not the essence of the soul, for a thought is an act, and since one thought succeeds another that which remains during this change must necessarily rather be the essence of the soul, since it remains always the same. The essence of substances consists in the primitive force of action, or in the law of the sequence of changes, as the nature of the series consists in the numbers.”

 

The nature of a substance is to act; if it would cease to act it would cease to exist. To what end does it act? It acts according to an inner law bestowed upon it by God and which lead to the orderly production of a series of states of the monad. Each of these states of a monad which are produced according to an inner law are representational states and the production of these states occurs in harmony with the states or the changes that occur in other monads. Thus no change within a monad occurs by chance; they occur in accordance with a pre-established harmony between an infinite numbers of monads. Every monad represents every other monad in the world from its own distinctive point of view and this distinctive point of view is what individuates a monad and explains the difference of one monad from another. No two monads can share the same point of view.

The representative states of a monad are of three types: a) perception b) appetition and c) apperception. Perception is simply representation which is defined by Leibniz thus:

“One thing expresses another (in my sense) when there is a constant and regular relation between what can be said of the one and what can be said of the other. It is thus that a projection in perspective expresses the original figure'” (Letter to Arnauld).

 

Perception is a state that expresses or represents every other monad according to the law of pre-established harmony without which there would be no order in the world of monads and hence no constant and regular relation for monads are ‘windowless’ – they do not interact with one another. Appetition is an ‘internal principle which produces change or passage from one perception to another’ (Monadology 15). Consider an arrow moving in one direction. It wouldn’t change course till something obstructs its passage and forces it to change course. Similarly a monad will be stuck with one perceptual state only if there is no internal force that does not obstruct it and allow passage to another perceptual state. Leibniz distinguishes his theory of force from the scholastic theory and Cartesian theory on grounds that it is neither motion nor a potentiality for motion but something in between – a striving for something (this is similar to conatus in Spinoza’s theory). Apperception is consciousness or thought. When a perceptual state is accompanied by thought we become conscious of it and it becomes possible to acquire knowledge. Self-Consciousness thus for Leibniz is an achievement or a development in the state of a monad; contra Descartes it is not simply present as a primitive state to us. In Monadology.30 Leibniz says:

“It is by the knowledge of necessary truths and by their abstract expression that we are raised to acts of reflexion which make us think of what is called "I," and observe that this or that is within us: and thus, in thinking of ourselves, we think of being, of substance, of the simple and the compound, of the immaterial and of God Himself, conceiving that what is limited in us is in Him without limits. And these acts of reflexion furnish the chief objects of our reasoning.”

Distinguishing between perception and apperception also helps Leibniz to account for the existence of mind in deep sleep state. In New Essays Leibniz elaborates on his theory of petites perceptions:

“The perceptions are still there, but having lost the attractions of novelty, they are not strong enough to claim our attention and memory, which are directed to more interesting objects. For all attention requires memory; and often, when we are not, so to speak, warned and directed to take notice of certain of our own present perceptions, we let them pass without reflexion, and even without observing them; but if someone immediately afterwards draws our attention to them, and speaks to us, for instance, of some noise that has just been heard, we recall it to ourselves and perceive that a moment ago we had some consciousness of it. Thus there were perceptions of which we were not aware at the time, apperception arising in this case only from our attention having been drawn to them after some interval, however small.”

 

Even though thought is not the essence of the soul; action is and even in deep sleep state the mind is continually producing perceptual states even though we are not conscious of these.

There is an interpretive difficulty here – if apperception is taken to be consciousness then perceptual states would be unconscious states of the soul. If perceptual states are taken to have minimal level of consciousness then there is no unconscious within Leibniz’s philosophy as Wundt believed. What then is the status of petites perceptions? Leibniz’s views are not clear on this matter but from his principle of continuity which says that no changes occur in a leap we can infer that perceptual states of the soul must have some minimal amount of consciousness to be eventually transformed through attention and memory into a self-conscious state. An unconscious would in Leibniz’s view would then be a confused or indistinct perception.

Coming to substance and attributes in Discourse on Metaphysics Section 8, Leibniz draws the distinction between substances and attributes:

“We must consider, then, what it means to be truly attributed to a certain subject. Now it is certain that every true predication has some basis in the nature of things, and when a proposition is not an identity, that is to say, when the predicate is not expressly contained in the subject, it must be included in it virtually. This is what the philosophers call in-esse, when they say that the predicate is in the subject. So the subject term must always include the predicate term in such a way that anyone who understands perfectly the concept of the subject will also know that the predicate pertains to it. This being premised, we can say it is the nature of an individual substance or complete being to have a concept so complete that it is sufficient to make us understand and deduce from it all the predicates of the subject to which the concept is attributed. An accident, on the other hand, is a being whose concept does not include everything that can be attributed to the subject to which the concept is attributed.”

 

The notion of a subject involves all its predicates but not vica versa. 

 

 Next we come to the degree of clarity and distinctness of representational states. In his ‘What Is an Idea’, Leibniz defines an Idea thus:

“First of all, by the term idea we understand something which is in our mind.”

This distinguishes Ideas from traces of sense-impressions which are really in the brain. Next:

“In my opinion, namely, an idea consists, not in some act, but in the faculty of thinking, and we are said to have an idea of a thing even if we do not think of it, if only, on a given occasion, we can think of it.”

 

And to say that an idea is innate is to say:

 

“That the ideas of things are in us means therefore nothing but that God, the creator alike of the things and of the mind, has impressed a power of thinking upon the mind so that it can by its own operations derive what corresponds perfectly to the nature of things. Although, therefore, the idea of a circle is not similar to the circle, truths can be derived from it which would be confirmed beyond doubt by investigating a real circle.”

 

We will come back to the theory of innate ideas later. For now we need to understand that no two monads can share the same distinctive standpoint from which they represent the world for otherwise they would be the same. This distinctive standpoint is understood in terms of a quantity of perfection found in the monads and which is intrinsic to a monad. Every monad exists within a continuum possessing a certain grade of perfection from which it differs from every other monad and within the series of monads the next one would possess a level of perfection a notch higher than the previous one in the same series. This degree of perfection signifies the extent of clear and distinct perception that the monad is capable of having. Every monad since it represents every other is not thereby conscious of the entire series of monads for slight imperfection clings to every monad except God. Hence in some measure every monad would have a confused or obscure perception otherwise it would be omniscient. The idea is well expressed by Robert Latta (1898):

 

“Confusedness is simply a low degree of distinctness: the more perfect any perception or representation is, the more distinct is it, while the less perfect it is, the more is it confused. Thus the differences among the Monads consist entirely in the various degrees of perfection or distinctness with which they perceive or represent the universe. But as each Monad actually represents the whole universe, however confusedly or imperfectly, and as each is essentially a force or living principle, proceeding, by its own spontaneous activity, from one perception to another, the distinct and the confused are not essentially separate from one another, but it is possible for the confused perception to unfold into distinctness. Each Monad contains the whole more or less confusedly within itself, and by its appetition may rise to a more perfect state. Each Monad contains as it were enfolded within itself all that it is to be. It is 'big with the future.' It is like an exceedingly condensed algebraical statement which can be indefinitely expounded: somewhat like the symbol n in the problem of determining the relation between the lengths of the diameter and circumference of a circle, with this very important difference, that the Monad reads itself off. An Omniscient Being could see the reality and history of the whole universe within the lowest Monad.”

 

Here certain further terminological clarifications are required. I shall follow here Leibniz’s Meditations on Knowledge, Truth and Ideas:

 

Knowledge can be divided into clear and obscure:

 

Obscure Knowledge: Does not suffice for the recognition of the thing represented.

 

Clear Knowledge: Suffices for the recognition of the thing represented

 

Clear Knowledge can be confused or distinct:

 

Confused: Ability to distinguish something on the basis of sense-perception but with no idea of its defining characteristic. The perception of colour is for instance confused because even though it is taken to be a simple sensible element in sense-perception it is still something that is composed of parts which though represented within a monad is represented distinctly. Whenever we have some perception where the parts of the thing perceived from indiscriminately grouped together or in other words we are not aware of the parts that compose it but which can be revealed through analysis; then we have a confused perception.

 

Distinct Knowledge: When we know the real definition of something. We shall elaborate on this later.

 

Distinct Knowledge can be adequate or inadequate and symbolic or intuitive:

 

Adequate: Defining marks are known distinctly

 

Inadequate: Defining marks are known confusedly

 

Symbolic: Concepts with parts obscurely understood

 

Intuitive: Concepts whose parts are understood simultaneously with the whole. Primitive concepts are understood by themselves for they are simple and hence can be known only through intuition.

 

Only God’s knowledge can be completely adequate. Since some imperfection always accrues to the monads their knowledge will always in some part be obscure and confused.

 

We now come to the basis on which Leibniz distinguishes between truths of facts and truths of reason. In his First Truths Leibniz says that a simple primitive concept is that of identity or what comes down to the same thing the law of non-contradiction. A Truth of Reason either asserts an identity or is reducible through analysis to an identity. Such a proof will be a-priori or independent of experience. From this Leibniz infers his predicate in subject principle which says that truth is nothing but a certain connection between subject and the predicate. This connection is identity. Next Leibniz deduces his Principle of Sufficient Reason which says that ‘nothing is found without a reason’ and ‘there is no effect without a cause’. For every predicate we have to find its ground within the subject to which it belongs otherwise that would imply that all Truths are not identities or are not reducible to identities. Note that the notion of a reason is broader that the notion of a cause because Leibniz says that we can demand a reason for the existence of eternal things too. But both are understood in terms of inherence of a predicate within a subject.

 

Next Leibniz deduces his Principle of Identity of Indiscernibles which says that ‘there cannot be two individual things which differ only numerically’; otherwise there would be something in nature for which there is no reason i.e. why should there be two things in nature that differ only numerically. It should be possible to give some reason of their difference from one another and this reason can be found only within their nature. Since every predicate belongs to its subject necessarily (identity being a necessary relation) no two subjects can share the same predicates and hence there cannot be ‘no purely extrinsic denominations which have no basis at all within the denominated thing itself’. The Law of Continuity is a corollary of this principle.

 

This implies that a ‘complete or a perfect concept of an individual substance involves all its predicates, past, present and future’. To this Arnauld objected that all that would happen to Adam for instance would follow from a fatal necessity destroying the chance of freedom. Leibniz’s reply in effect is that an essence is the object of God’s Understanding and existence is the effect of God’s Will or God’s decrees. God’s decision regarding which predicates would be found within the concept of Adam depends on taking into consideration all other possible individuals along with Adam. There is only a hypothetical necessity involved here because God has to consider the best of all possible worlds to actualize. And Adam would actualize the contents in the concept of Adam only if God decides to actualize it within the scheme of things. It is important to note that given the Principle of Identity of Indiscernibles it follows that there can be no extrinsic denominations; all properties of a substance are intrinsic to it and individuate it. Hence in modern terminology there cannot be any possible world which would have an Adam but where he is not the first man. All properties of Adam necessarily follow from the nature of Adam and are likewise contained within the concept of Adam but no one save God can deduce all predicates contained in the concept of the subject. 

 

But here Arnauld posed a dilemma for Leibniz. Either the notion of Adam is prior to the Divine Will in which case the predicates which follow from the notion of Adam would be intrinsic and necessary because they would be within Divine Understanding and Leibniz admits that essences are objects of Divine Understanding prior to any consideration of the Will. Or else they are posterior to Divine Will or in other words created by the Divine Will in which case the connexion between the predicates and the subject will neither be intrinsic nor necessary. To this Leibniz replies that the connexion here is intrinsic without being necessary. It is not necessary because what predicates Adam would have in the course of its existence is decided by the Divine Will; those predicates are not so much the consequence of the essence of Adam but of the essence of Adam along with a possible decree of God. This presupposes the prior consideration of Adam’s compatibility with the other notions and these possible predicates that he may have is known a-priori under the condition of the possible decrees Adam may actualize when he would exist. Hence the possibility that follows from the essence and the possibility that follows from the concept of Adam are different. The concept of Adam is compossible because the existence of Adam does not follow from the essence of Adam and requires the institution of Divine Will apart from Divine Understanding. The possibility of an essence is a consequence of the law of non-contradiction while the possibility of the concept of Adam follows from taking into consideration its compatibility with other concepts which would be combined together within a single world.

 

Now we can distinguish between truths of facts and truths of reason. Truths of reason knowable a-priori require only true identities. All truths of reason are either identities or reducible to identities. But truths of facts are contingent and knowable via experience. They cannot be deduced straightforwardly from the concept of a subject contra Descartes and Spinoza. Nevertheless they are intrinsic to the subject or have their reason or ground for their existence within the subject. The reconciliation of these apparently contradictory notions requires us to reconceive the notion of identity. In the case of truths of facts identities are not self-evident and do not simply require attending to their presence within the subject but on the other hand require us to take into consideration the compatibility of the predicate with the notion of every other subject. Thus identity of predicates in case of Truths of facts requires reference not only to its own subject but also to every other subject. These identities are governed not simply by the principle of non-contradiction but by the principle of pre-established harmony. Since every monad expresses another and since it is the essence of every monad to express every other from its own distinctive point of view; the identity of every monad contains an explicit or implicit reference to every other. This requires change within traditional logic which is a logic of being not of becoming. Martial Gueroult (1946) has expressed this well:

 

“It does not suffice for Leibniz to perceive in a general way that a certain mode is linked to the substance and necessarily posited by it; he also needs to conceive why a certain mode must occur at a certain determined moment in time. For a state receives the full determination of its content only through its complete connexion with all the other parts of the whole, therefore through the place which is its own in space and in time. Thus the fundamental requirement of rationalism, to reduce individual reality to a system of conceived relations, can no longer be realized simply by conceiving how the particular predicates are, in a general way, the con-sequences of the subject to which they belong. That was what rationalism had been content with heretofore, when it tried to establish the fundamental logical connection of things, and that is why it took geometry for its model: just as it is included within the concept of the triangle that the sum of its angles equals two right angles, so the foundation of reality which embraces everything, engenders necessarily all the particular determinations.”

 

And,

 

“The logic of the school considered concepts as immobile entities given once and for all: the qualifications which belong to a concept are its own in abstracto, in itself and by itself. There is no question of a development in which they would participate, nor of their changing and progressive production. Thus, what follows from the nature of a thing belongs to it in an unchangeable fashion and for all times. Leibniz on the contrary has taken hold of the problem of change and has conceived it as a logical problem, and the concept of subject assumes then a new meaning. It can no longer be, as it had been for formal logic, the passive and inert support of multiple determinations, but it is conceived as the active principle which positively creates them. It is only thus that the logical subject is transformed into a metaphysical substance, that it is thought of as the source and original foundation of the determinations which are to proceed from it in the future according to a pre-established law. Thus the idea of vital development renews the logical concept. On the other hand, logic becomes more profound so as to account for this vital development and submit it to a rational norm. The notion of vital development is united with the adage: praedicatus inest in subject; differential calculus, by providing the concept of the law of the series, which accounts for all details through time, makes the rational coextensive with the becoming.”

 

The relation between whole and parts thus should be understand as between the sign and the signified. The part or the monad expresses the whole howsoever imperfectly and the whole is expressed within each and every part. Cause-Effect relation is also understood in terms of expression. One monad expresses another but when one expression is confused in relation to the other then the former confused perception is seen as the effect and the more distinct perception as the cause. Hence we think that a certain external object is the cause of the sense-experience we have. We take the external object to be active and the sense-experience to be passive. The relation between cause and effect is the relation between different monads and their expression of each other. Hence the relation of cause-effect lacks analytic necessity but has synthetic necessity (to introduce Kantian terms) which is understood in terms of the pre-established harmony or the compatibility of everything with everything else instituted by God in each and every monad. The substance or the monad however contra Descartes is still a source of force or action even though the direction comes from an inner law created by God. Hence such a substance does not require God to constantly re-create it but can be a secondary source of action. Leibniz also goes past Spinoza’s fatal necessity since God’s Will requires God’s Understanding to choose the best of all possible world. The order of synthetic truths is not a necessary consequence of the nature of God but the necessity involved here is a moral necessity rather than a metaphysical necessity.

Finally we come to the topic of innate ideas. In Leibniz’s system the Idea of God and Extension do not reflect simple essence. Descartes has been too hasty to come to the conclusion that an Idea is simple appealing merely to clear and distinct Ideas. An atheist however would protest that he has no clear Idea of God to which Descartes’s response would beg the question unless he shows how the atheist can have similar experiences. Hence the clear and distinct criteria of truth lacks bite and is empty. Human thought is symbolic and more often than not we take an Idea to be simple which however is composed of parts which only further analysis can reveal. We can thus understand Leibniz’s criticism of Descartes’s ontological argument. To deduce the existence of God from the Idea of God requires first to prove that the Idea of God is possible and this Descartes has simply assumed because he takes it for granted that we can talk and think about God and thus we have the Idea of God. But it is something that requires demonstration. The Idea of God is shown to be possible by Leibniz by defining God as the subject of all perfections and then providing a proof that all perfections may be present within a subject without contradiction. The demonstration presupposes that the Idea of God is itself composed on prior notions of perfections which Leibniz understands to be positive, simple and indefinable. All these perfections must have a reason grounded within their subject and this subject is what we call God (Two Notations for Discussion with Spinoza, On Universal Synthesis and Analysis or the Art of Discovery and Judgement and Meditations on Knowledge, Truth and Ideas). We have a real as opposed to nominal definition of something when we can demonstrate its possibility or show those properties that tell us that something is possible.

The concept of extension also is not simple as Leibniz argues:

“For an extended being implies the idea of a continuous whole in which there is a plurality of things existing simultaneously. To speak of this more fully, here is required in extension, the notion of which is relative, a something which is extended or continued as whiteness is in milk, and that very thing in a body which constitutes its essence; the repetition of this, whatever it may be, is extension.”

 

Simple Truths are truths of identities for Leibniz. Against Descartes he points out that in addition we have truths of facts which require real grounds not just ideal grounds within understanding. Since these truths are governed according to a pre-established harmony they presuppose God as their source. Against Locke Leibniz points out that there are Truths of Reason that cannot be known through sensible-experience.

In Leibniz’s case it is enough to define innate ideas in terms of objects of understanding. We have seen for Leibniz to have an innate idea is to have a faculty or a disposition to recognize certain Truths. But unlike in the case of Descartes we do not need to demarcate these Truths in terms of their cause being God. It is sufficient to point out that they are in understanding alone. The reason is first that essence in Leibniz are eternal and are objects of God’s understanding and are not created by God. Second, Descartes does not distinguish between truths of facts and truths of reason. The former too have their source in human understanding hence we found it difficult to exclude sense-experiences merely by appealing to the nature of the thinking substance. But since Leibniz draws this distinction it is enough to point out that these truths are found within understanding alone. Third, Leibniz always begins with the perfect concept which is the object of God’s Understanding (Letter to Arnauld). For Leibniz the difference between human and divine understanding should be understood to be a difference in quantity not in quality. Hence he finds no problem to begin with a perfect concept even though human beings do not have a perfect concept. But to ensure simplicity of primitive concepts in Leibniz we do not need to add any clause about Divine Understanding.

We can also see how Leibniz steers the rationalist program from Gassendi’s and Malebranche’s arguments. Leibniz is in agreement with Gassendi and Malebranche that the Transparency Principle (Descartes: “….. Nothing can be in me of which I am entirely unaware.”) cannot be held and that thought is not the essence of the Substance. The soul can have petite perceptions of which it is not conscious. Self-consciousness is achieved through knowledge of principles or reason and it does not consist in beholding the vision of the self but necessarily involves reference to a world outside. The inward consciousness is achieved through the external consciousness – the two being intimately linked together.

But the objections raised against Cartesian theory of substance cannot be raised against Leibniz. First, because simple truths are for him either identities or reducible to identities they have a claim to being self-evidently true and knowable a-priori. Second, strictly there is a distinction between an essence and a substance. While the former is absolutely simple, the latter is only relatively simple. The reason is that existence cannot be deduced from essence and the concept of Adam for instance is both the object of Divine Understanding and subject to possible decrees of God which is the cause of existence and is added to an essence to transform it into a substance. The distinction between substance and its modes is not drawn by Leibniz on basis of possibility of one existing without the other but on basis of conception of the substance being much more inclusive than that of an attribute. Hence there is a strong intimate tie between a substance and its modes – the latter is only an expression of the substance in accordance with an inner law of sequence of changes and the substance cannot exist without having some qualities or other. It necessarily is active. Third, Leibniz draws the distinction between truths of reason and truths of facts. While the condition of tracing every property of a substance back to its ground in the substance is something Leibniz has in common with Descartes still he does not believe that even though the connection between a subject and predicate is of identity – we still cannot be aware of this identity in every case. This is to say that in case of truths of facts we cannot deduce the property from the substance or simply from the definition of the thing like in the case of deduction of the Pythagorean property from the definition of the triangle. Certain predicates are found within the subject due to its relation to every other monad and its expression of every other monad instituted within every monad by God’s Will in accordance with a pre-established harmony. Only God can read the reason of every predicate that can be found within a subject. While a perfect concept contains all predicates an entity can have in course of its existence only God is capable of deducing the reason for all such predicates from the concept of the substance. Human Beings lack that capacity. The deduction of the predicate from the concept of the subject is a regulative ideal for science but not one that is achievable. Since monads are infinite in number the attempt to trace every predicate back to the subject would require an infinite analysis for the process would implicate every other monad that is represented within a single monad. Hence the monads themselves cannot be the reason for the entire series of monads; only something outside the series of monads can provide the reason for its existence. This reason is God. Fourth, the practical inability to trace the source of truths of facts to monads themselves does not compromise the rationalist program because it is a regulative ideal. And unlike Descartes Leibniz believes that the primary purpose of philosophy is not analysis but synthesis. Analysis traces back a predicate to its ground in the subject. There is a reason that a predicate is found in a subject and not in another. But as we have seen this is practically impossible in the case of truths of facts for a sufficient reason for their existence in the subject would require an implicit reference to other monads which are infinite. Even Spinoza’s infinite substance cannot do justice to the concrete reality which becomes unreal or an abstraction because of the emphasis on the greater reality of the whole over the parts. Synthesis on the other hand begins with the principles and attempts to understand the reason for the existence of things in accordance with those principles. Consistent with his philosophy there are two sets of principles required for this purpose. Principles of understanding which are a-priori – the ideal ground for the existence of the world and Principle of Sufficient Reason – the sufficient reason for the existence of the series of monads we have seen is God and the order of experiential truth depending on a pre-established harmony depends on God’s benevolence and Wisdom for these truths are a matter of choice and not metaphysical necessity but moral necessity. Hence in Leibniz’s philosophy we come across a duality between ideal grounds and real grounds. Kant noted this point and also the relation with his own philosophy. In his reply to Eberhard he elaborates on Leibniz’s Pre-Established Harmony:

“Hence the connexion between understanding and sense in the same subject can be understood according to certain a priori laws, as well as the necessary and natural dependence of sense upon external things, without sacrificing external things to idealism. For this harmony between understanding and sense, in so far as it renders possible a priori the knowledge of universal laws of nature, criticism has given as a reason that without this harmony no experience is possible But we can give no reason why we have just such a kind of sense and an understanding of such a nature that through their combination experience is possible; and further we can find no reason why they, as completely heterogeneous sources of knowledge, always so completely harmonize in rendering possible experiential knowledge in general and more especially (as the Critique of Judgment shows) in rendering possible an experience of nature, under its manifold special and merely empirical laws, regarding which the understanding teaches us nothing a priori. Neither we nor anyone else can explain how this harmony is as complete as if nature had been arranged expressly to suit our power of comprehension. Leibniz called the principle of this union (especially with reference to the knowledge of bodies and in particular of our own body as a middle term in this relation) a pre-established harmony. Manifestly he did not in this way give an explanation of the union, nor did he profess to explain it. He merely pointed out that we must regard the order established by the supreme cause of ourselves as well as of all things outside of us as involving a certain conformity to end.”

 

The division between sense and intellect is not as radical in Leibniz as in Kant. For Leibniz sense perception is a confused perception capable of becoming more distinct by the operation of the intellect. But knowledge that may be acquired through experience cannot be acquired through reason and vica-versa. The ground for the truth of facts knowable through the senses and the ground for the truths of reason are different. One can be traced to Divine Understanding and are necessarily true both for us and for God and another to Divine Will depend on God’s choices and hence are only contingently true. The predicates involved in both have a reason or ground in the subject though in cases of contingent truths we are not capable of knowing these reasons absolutely. They can ultimately be only referred back to God. We can notice here a tension in Leibniz’s philosophy – while he requires a difference in ideal and real grounds yet he also seeks their greater unity which eludes him. We will have an opportunity to see that Leibniz juxtaposes the Principle of Non-Contradiction with the Principle of Sufficient Reason without being able to reconcile both.

 

However we can see now the inner dialectic of the rationalist program quite clearly. It began with the demand to trace everything that exists back to its essence in such a way that it could be deduced from the essence itself. This required an inner contemplation of Ideas and the ability to see clearly and distinctly the presence of a property in its essence. A demonstration is nothing but a series of simple intuitions which grasps the determination of a property of a determinable essence. The Principle of Non-Contradiction is paramount here. We have an Idea if no contradiction in involved within it and all truths can simply be deduced from this Idea. However this elegant picture receives a setback with Gassendi and Malebranche pointing out that the deductive ambitions are not achievable. For all its emphasis on intelligibility there is an obscurity with the rationalist theory. The obscurity in the notion of substance and the relation between substance and its attributes has epistemological repercussions. The ability to trace every truth back to its principles requires greater grasp of the principles themselves. But this is absent from the Cartesian Paradigm for it requires grasping the essence of a thinking substance that is capable through an inner awareness to grasp all truths or principles found within it or are innate to it. But this capacity for self-illumination to uncover the principles can never be proved for we are unaware of the nature of this substance. And this piece of ignorance is because the notion of substance itself is obscure. The fate of the Cartesian Program is sealed with Leibniz drawing the distinction between truths of facts and truths of reason and demonstrating that the simple essences Descartes believes he is aware of are not really simple and that he took the analysis to be too simple a task to accomplish which it is not. However he also rescues the rationalist program by taking deduction of all predicates from the concept of a substance as a regulative ideal and emphasizing synthesis to a greater extent than analysis for we can be aware of reasons only through application of principles to matters of fact. Even though Spinoza can be seen as emphasizing synthesis over analysis Leibniz has a broader spectrum of principles for ideal truths and real truths and unlike Spinoza he does justice to the reality of the parts as well as of the whole and does not seek to reduce one to the other. But the question is how successful is Leibniz in establishing a harmony between sense and the intellect?