For the class in Modern Philosophy I'm taking this semester, we have to write 15 two-paged papers (minimum) on philosophers such as Descartes, Hume, Locke, and Leibnitz. In this essay, I wrote about select passages in Leibniz's Letters to Arnauld and his Primary Truths. The following is my submission:
Leibniz wrote Primary Truths as a brief explanation of the foundation and reasons for his philosophical beliefs. Beginning with the idea that truth is a proposition whose predicate is contained in the subject, Leibniz inferred that nothing is without reason – not even eternal truths – as nothing can be validly resolved apart from the law of identity or non-contradiction.
Leibniz used the idea that predicates are contained in a subject to support his definitions of man’s essence and [compatibilistic] free will. Man is his predicates, said Leibniz, insomuch as all predicates are contained in the subject (man). Leibniz, who was a determinist, also believed that nothing corporeal could necessitate a metaphysical action on man’s will; man, then, is said to be free insofar as his actions pertain to intrinsic reasoning or desires. These are certainly determined, however, by God, who chose to create particular men from an infinitely many possible men. Moreover, as man’s essence or substance would be indeterminate if only regarded as a finite conglomeration of [past or present] predicates – for one could conceptualize infinitely many future counterfactual situations in which such men make different choices – man’s substance must contain all future predicates. Essence, then, is unchanging.
This in turn led Leibniz to affirm that all things correspond perfectly, since all relations between substances are determined by the essence of said substances. Each substance expresses in varying manner the cause of them all: God. Leibniz appeals to this cohesion to substantiate his qualification of Occasionalism in concert with his affirmation of concomitance. Leibniz believed that a true union exists between the soul and body such that when, for example, the body becomes afflicted, the soul naturally experiences pain or grief. The mind, on the other hand, can move the body as a real cause, but only so far as God created the mind with such a capacity and certainly determined that the mind would act in such a manner. In this latter sense, Occasionalism is true. Leibniz uses this qualification to purport miracles as acts of God in which God moves a substance to do more than the capacity with which God bestowed upon it in its first state.
A final important point Leibniz makes is that all corporeal bodies can be divided. Leibniz uses a block of marble as a simple example of his meaning: the block may actually be considered only a mass of stones, and these mass of stones only a mass of atoms, ad infinitum, such that any substance is actually a collection of many substances. This bears relevance to the way in which we perceive bodies as substances and seems to validate Leibniz’s claim that “with the exception of men there is nothing substantial in the visible world.” Any such designation would arbitrary.
This argument seems to be incompatible with Leibniz’s insistence that bodies may be true causes. If any body is composed of infinitely many subdivisions, for one body to affect another body, infinitely many reactions must occur in time, which is impossible. Another possible criticism of Leibniz’s philosophy is that his understanding of man’s essence is such that man cannot comprehend himself. Man does not know his future predicates, so God literally knows us better than we know ourselves. It does seem that Leibniz attempts to explain we can have an apprehensive knowledge of ourselves such that we can rationally hypothesize how we would act in any given circumstance, but such hypothesizing could not possibly account for the infinite number of possible variables which could affect the way in which we perceive ourselves. Leibniz may bite the proverbial bullet and maintain the cohesion of his affirmations, however.