Rationalism - Spinoza, Descarte, Leibniz

While Descartes believes that there are only two substances that can be trusted, mind and body, Spinoza believes that we are all part of the same substance and mind and body are one. Being against dualism, due to it not being a progressive line of thought, Spinoza considers thought and extension as two attributes of the one substance. Attributes are the essential characteristics of Substance. Substance, to Spinoza, ‘is that which is in itself and is conceived through itself.’   Along side Spinoza’s concept of substance, which is highly abstract, is the principle of sufficient reason. This principle states that there is sufficient cause for everything, no exceptions granted. If anything exists, it is this substance. Thus entails that our world could not exist if everything depended on something or someone else to exist. Spinoza believed that there was one entity that was responsible for its own existence, God.

In stark contrast to Spinoza’s concept of one substance, is the notion that substance is infinite. Leibniz puts a different spin on substance, believing that the fundamental constitutes of reality must be absolutely minimal, even more so than atoms. Leibniz calls this substance, Monads. Monads have no shape, size or parts. We must begin to understand what a monad is by beginning from the idea of a complete concept.  A substance/monad is that reality which the complete concept represents. A complete concept contains within itself all the predicates that are true of the subject of which it is the concept, and these predicates are related by sufficient reasons into a vast single network of explanation.  So, relatedly, the monad must not only exhibit properties, but contain within itself 'virtually' or 'potentially' all the properties it will exhibit in the future, and also contain the 'trace' of all the properties it did exhibit in the past. In Leibniz's extraordinary phrase, found frequently in his later work, the monad is 'pregnant' with the future and 'laden' with the past  (Monadology, p22).  All these properties are 'folded' up within the monad, and they unfold when and as they have sufficient reason to do so.  (Monadology p61)  The network of explanation is indivisible - to divide it would either leave some predicates without a sufficient reason, or merely separate two substances that never belonged together in the first place.  Correspondingly, the monad is one, 'simple' and indivisible.

Everything we perceive around us, which is a unified being, must be a single monad.  Everything else is a composite of many monads.  My coffee cup, for example, is made of many monads (an infinite number, actually).  In everyday life, we tend to call it a single thing only because the monads all act together.  My soul, however, and the soul of every other living thing, is a single monad which 'controls' a composite body.   Leibniz thus says that at least for living things we must posit substantial forms, as the principle of the unity of certain living composites.  My soul, a monad otherwise like any other monad, thus becomes the substantial form of my otherwise merely aggregate body.

Thus the entire course of the universe, the total aggregate of substances, or monads, across space and time are one and all contingent.  There are other possible things, obviously; but there are also other possible universes that could have existed but did not.  The totality of contingent things themselves does not explain themselves.  Here, the principle of sufficient reason applies.  There must be, Leibniz insists, something outside the totality of contingent things that explains them, something that is itself necessary and therefore requires no explanation other than itself.  In other words, the properties of every monad in the universe, just like the properties within any one monad, are all interconnected in a vast network of explanation, according to the law of sufficient reason. Yet what is the reason for the whole set of monads? What explains the existence and nature of the universe itself? God, then, is the necessary being which constitutes the explanation of the contingent being, why the universe is this way rather than any other.

Leibniz has four major arguments for the existence of God, tying in with his monadology, and each one casts God as being distinct and separate from his creations each of which are comparable to Descartes arguments. Thus the existence of God and the idea of how and why he exists is a major contention point between Descartes/Leibniz and Spinoza. In the first part of Ethics, Spinoza asks ‘What exists?’ in answer to his question he considers that ‘Except God no substance can be granted or conceived.’ Thus, whatever we perceive must therefore be in God and he must always exist for everything to be conceived.  Substance, for example, he defined not only as existing in itself but also as ‘conceived through itself.’ This places a severe limit on the possibility of interaction between things, since Spinoza delared that causation is a relation of logical necessity, so that knowledge of the effect requires knowledge of its cause. Few will disagree that God is a substance with infinite attributes, but this definition carries some surprising implications in Spinoza's view of the world; notice also that freedom, according to Spinoza, just means that a thing exists and acts by its own nature rather than by external compulsion.

Since causal interaction is impossible between two substances that differ essentially, and no two substances can share a common attribute, it follows that no substance can produce genuine change in any another substance. Each must be the cause of its own existence and, since it cannot be subject to limitations imposed from outside itself, must also be absolutely infinite. Things that appear to be finite individuals interacting with each other, then, cannot themselves be substances; in reality, they can be nothing more than the modifications of a self-caused, infinite substance. And that, of course, is God.

Prior to Spinoza’s idea for God, Descartes had developed his arguments for God. Referred to as the Ontological Argument, he had three main arguments for the existence of God and each one dealt with God and his creations being distinct from each other. Descartes first sets out the premise that God is the cause for the idea of himself. Descartes then realises that, as he is not the cause of his own existence, he must depend on some being that does not rely on anything for it to exist. God is the reason for the ‘existence of the mind that contains God.’ The third argument is the ontological argument. Descartes believes that since ‘God possesses every perfection and as existence is a perfection that only God can obtain, God must therefore exist.’ He gives the example that since we can perceive God; it is impossible to not conceive him, just as it is to not be able to conceive of a square having four sides. The ontological argument ‘proves’ that at least one thing exists, God. Spinoza takes this argument one step further and believes that it shows that ‘at most’ one thing exists and so anything that does exist must exist ‘in’ God.

There are strands of similarity between each philosopher, however the division between the three major rationalists is more distinct than their likeness. If rationalism were to be a major philosophical belief that were to last, not just influence succeeding philosophers throughout the ages, the consistency of arguments between these philosophers would have had to have been unified. However, their simple contradiction of each other and their tangent of thoughts, although undermines the viability of rationalism, leads the way for the next generation of philosophy, Empiricism.