Aristotle bases his philosophical program on the study of nature, and specifically the changes objects in nature are able to undergo. This is opposed to his metaphysics, which is only able to come afterward, as it broadly addresses all possible beings, and not just those found wholly in nature. We might at first seem definitively capable of studying these changes in natural things by comparison to the seemingly far more speculative metaphysical objects, which we do not find so clearly in the world all around us. Even in Aristotle’s time though, there were serious dilemmas which they felt needed to be answered concerning the possibility of change. Plato held that the real forms, each being individually idealized through itself, could not then undergo any kind of change, and so was one of the first to claim that change was only possible in the appearances brought about by the natural world. However, Parmenides suggested rather that change was not possible at all. Through Aristotle’s account of this argument, it can be seen that in change a thing must arise either out of what it already is, which seems impossible as this presupposes a simple identity with itself and so no change can be involved, or from what it is not, and how should anything go about arising out nothing?
Of course he still seeks to offer an account for change and so rather works to found this on his notion of coming to be. In this way he works to answer what it means for both change to occur and also how a thing comes in to existence at all. In the case of Plato’s notion of change there are only two elements put forward, what comes before and what it evolves in to. Aristotle wants to involve an additional entity in this process, namely the very subject on which each change undergoes, and so every description of a change must also incorporate just such a notion where Plato’s conception mistakenly stopped short at. In this way, it can be seen that an amount of bronze might be formed in to a statue, and that there is a subject which persists throughout by way of the underlying matter, such that it changes from its shapeless form in to something which we would observe a certain order in by design of the sculptor. Conversely, this form may be weathered away over the centuries by lack of human intervention, such that it reverts the process of change from its structured form back in to another shapeless mass. In this way it can be seen that change does not always necessitate a pair of opposites as suggested by Plato, but instead just a matter on which some form can be applied and a simple lack of this form in its alternate state. This avoids the difficult method of attributing the existence of an exact polar division between each end of every change, as now seems unnecessary having put forward these consistent notions of creation and destruction as certain processes of change. As rather than simply morphing from one complete form in to another, the process admits to a compounding of phenomena occurring on each side, such that every object can be seen as a complex being, both admitting to its own form and lacking in others. Before the sculpting of the statute the bronze is not simply in a state of being “statue-less,” but rather itself contains a certain character in its own right by way of its underlying matter, the same complex form which it may again take in the statute’s eventual destruction. The statue itself is neither a complete form as it lacks in the very formlessness which exactly works to characterize the shapeless mass of bronze.
Descartes begins his own program on a broader principle of the basic search for sound truths in any place, which might not necessarily be first derived from empirical discoveries of the natural world. He believes rather that human wisdom can be applied toward a multitude of subjects, and so in focusing our attentions on the natural sciences alone, we may be omitting more fundamental discoveries which lie in relating such knowledge with other interconnected matters which make up the whole of compounded human knowledge as should properly be taken together. Moreover, it would seem that all the claims of the empirical sciences are subject to certain doubts, as we can only ever be so certain about the underlying process behind any given observed phenomena, and are often mistaken in such matters. Conversely, mathematics and geometry, having been arrived at through pure reason, seem to elude this problem altogether. We can not be even the least bit skeptical of such inferences arrived at by simple chains of deductive reasoning, as each consecutive step is to be found exactly in its presupposition, and so can only then go wrong by allowing this process of reasoning to become lost on ourselves entirely.
Alternative to the laws which Aristotle attempted to apply underlying the changing of the world, Descartes instead found that the world itself follows is subject to no laws whatsoever but is rather simply a matter of mechanistic interactions. In this way he removed the anthropomorphic sort of mind applied to each and every thing by previous philosophical notions, as if there were some sort of intelligence in the mass of bronze which demands it follow the complex process as accorded by the Aristotelian notion of change in the world through to completion in order that it may become a statute. Rather, Descartes would simply chalk this up to the sculptor’s beating away at the mass with whatever tool, and that really it has nothing at all to do with enacting its own change in any sense as previously put forward. This theory is founded on an idea of minute physical corpuscles each containing only a small number of properties which constitutes the entirety of causal interactions in the world, thereby disregarding the historical notion of form in its entirely.
In examining his own formerly held notion of gravity Descartes found that he was himself guilty of attributing intelligence toward objects which most definitively exhibit none, and so had to change his prior held views founded on the forms. It was long thought that gravity worked to move bodies toward the center of the earth as if they had some sort of guiding intelligence in order to carry out this active process. But he does not attribute intelligence whatsoever to entirely any passive thing such as an inert rock, and so we must account for the phenomenon of gravity, which surely takes place in either case, by some other method. He first rejected the prior idea of a vacuum-like space which bodies are present within, by founding space exactly on the extension of body itself, and disregarding the meaningless notion of there being a space without a body to fill it. In this he replaces his own notion of the vortex conception of motion, which avoids any attribution of intelligence to passive objects. Rather than each object on its own changing its position internally in regard to an unintelligible vacuum-like space, within which its motion could never itself be charted against the entirely identical infinite void, he only ever refers to motion through changes in the neighborhood among multiple objects, such that motion is always characterized relative to other bodies, and not merely against any space itself. In this way he accounts for the influence of gravity by suggesting that where previously was attributed an empty void is actually a space made up of many more corpuscles, just in a much lesser density than which makes up intelligible bodies. As we travel along our paths of inertial motion we are also subject to the force of weight of these bodies pressing down us, which hold us the surface of the earth, and which also hold the earth in its rotation around the sun, rather than shooting off in a straight line in to the cosmos as it initially tends towards.
Descartes considered that basing one’s scientific method entirely on the natural sciences alone was the cause for so many grave errors of the past and so wanted a different set of foundational principles from which his own excursion in to the natural sciences only as a secondary program derived in part on these founding principles. This would structure the observations of the natural world in a strictly rational way so as to prevent ourselves from making claims beyond the bounds of possible experience as Descartes believed had been the cause of so many distracting philosophical concerns of the past. In this way, he worked to apply the skeptical lens in as critical a way as possible against a series of truths which to him seemed conceivably foundational, in order to deduce which subset might properly be set forward so as to structure the rest of the sciences that would follow.
The cogito is distinct in so far as it alone among all potential founding principles seems to justify its truth on its very presupposition. In thinking of himself as a thinking being, Descartes finds himself to be inescapably thinking in some way, no matter that be in the case of the human being determined in the world as we commonly believe ourselves to be, or rather in such a skeptical scenario as a demon deceiving him by every intuition he has ever experienced, he still finds himself to be thinking in some manner. In any either case however, a presupposition does not allow for a properly justified belief as it only ever arises out of simple identities which do not seem at all to make for appropriate foundational principles upon which we will base the rest of the empirical sciences, instead largely resultant of a kind of compounding knowledge not possible through any apriori reasoning alone.