Transcription
René Descartes, more commonly known as Cartesius, is one of the main protagonists of the scientific revolution of the 17th century. This is thanks to his definition of the Cartesian method and his status as the main inspirer of the philosophical current of rationalism, which inaugurated the turning point of modern philosophy. The fundamental principle of his rationalism is the idea that the validity of knowledge resides in human reason and not in faith or the senses. The principle underlying this reasoning is the mathematical method. Mathematics is based on the presence of axioms, or evident principles that do not need to be proven, from which it is possible to arrive at particular truths. These axiomatic truths are defined as a priori ideas, which are valid a priori, that is, before experience itself. Because they are valid a priori, these ideas are also universal, belonging to everyone. In fact, they are also called innate.
This logical and rational method—starting from innate ideas and then arriving at individual truths through reasoning—can be applied, according to Descartes, to other fields of inquiry, such as metaphysics, physics, or ethics. Reason, therefore, is sufficient in itself to achieve universally valid knowledge. The first problem that Descartes poses is that of defining a method that makes the application of reason valid. If, in fact, the ideas produced by reason are valid in themselves, the reasoning that the individual applies starting from these ideas can be wrong, thus leading to error. The method developed by Descartes is based on four moments.
The first moment is that of evidence. Reasoning can, in fact, start only exclusively from ideas defined as clear and distinct, that is, not susceptible to doubt—ideas that are self-evident. Therefore, axiomatic truths. The second moment is that of analysis. By analysis, we mean the application of the deductive procedure; that is, one starts from the general problem to arrive at decomposing the individual parts. Then we have the third moment, that of synthesis. By synthesis, we mean a phase opposite to that of deduction, in which the inductive procedure is applied; that is, once the problem has been broken down into parts, we proceed to a recomposition that allows a solution to the problem. Finally, we have the fourth moment, which is that of enumeration. By this term, we mean nothing more than a verification, or a check of the various steps that have been carried out to eliminate possible errors.
Having defined this method to be applied universally to arrive at rational knowledge, Descartes goes on to describe his metaphysical vision, that is, of those first principles that are beyond nature and at the base of it. Cartesian metaphysics is based on the existence of two substances, or two bases of manifestation of reality: thought and matter. Descartes defines them as res cogitans and res extensa. Res cogitans is an incorporeal substance, conscious of itself and free. Res extensa, on the other hand, is corporeal, extended, unconscious, and determined mechanically. These two substances are at the base of all expressions of reality. The thinking substance is at the base of all those acts such as thinking and desiring. The corporeal substance, on the other hand, is the basis of all bodies. This duality of substance leads to talk of Cartesian dualism.
Two elements are important in this discussion: 1. Asserting that everything derives from a basic substance guarantees that ideas, on the one hand, and bodies, on the other, always have a foundation. Therefore, all a priori ideas have universal validity, just as the laws of physics are always valid. 2. Asserting that the two substances are separate serves Descartes to maintain that matter is totally autonomous from forces of other natures. Descartes can thus overcome Aristotelian finalistic physics, arguing that matter must be studied in its quantitative and not qualitative data, as Aristotle wants, and that it acts without any purpose, but only in a mechanical way.
Having established the existence of two substances, Descartes argues the need to demonstrate their existence. Knowledge, in fact, can only arise through doubt. The existence of the thinking substance is demonstrated by pushing doubt to its extreme. According to Descartes, in fact, it is necessary to doubt everything, including our existence and the existence of the world around us. This approach is defined as hyperbolic doubt. However, even by taking doubt to its most extreme radicality, one cannot doubt one thing, Descartes argues, namely the fact that the subject who is doubting is effectively doubting, therefore performing an action related to thought. In other words, doubt itself demonstrates the existence of a thinking subject. This conclusion is summarized in the famous statement: Cogito, ergo sum—I think, therefore I am. In doing so, Descartes places the foundation of knowledge on human reason itself. The Cogito demonstrates the existence of thought, but a problem remains: the existence of matter. The ideas produced by thought might, in fact, not correspond to a really existing nature. Descartes, in fact, argues that the world could be nothing more than a deception produced by a malicious genius. Therefore, to demonstrate the existence of the world, it is necessary to demonstrate the existence of a good God who cannot deceive man.
Descartes, therefore, sets out on the path of the demonstrations of God, but not with the aim of scholastic philosophy—that is, to demonstrate that the world reflects the Divine order—but to support the real existence of the world, of the nature around us. The demonstration of the existence of God also proceeds, in this case, from reason itself. Thought, Descartes argues, produces three types of ideas: innate ideas, which are those ideas present in man from the beginning, not derived from the outside; adventitious ideas, that is, those ideas derived from the outside, for example, the idea of a tree that arises from the sight of a tree; and finally, factitious ideas, those ideas that are formed in the subject himself and that have no correspondence with reality, for example, the idea of a flying donkey. The idea of God, Descartes says, belongs to the category of innate ideas, as it is the idea of perfection. This idea cannot be adventitious, as we never have experiences of perfection, nor is it factitious, as man is imperfect and therefore could not alone give birth to the thought of perfection. Following this reasoning, the conclusion is that if God is an innate idea, he must necessarily exist, otherwise man would not possess such an idea.
Because of the existence of God, Descartes can add a focal point: since God exists and is perfect, he is necessarily good, since goodness is a necessary attribute of perfection. And since God is necessarily good, he cannot deceive man, and therefore it can be concluded that the external world exists really. It cannot be the product of a malevolent genius. In conclusion, everything that appears clear and evident is true, as it is guaranteed by God. This means not only that nature exists and can be studied in its characteristics, but also that the Cartesian method, which must start from what is clear and evident, is effectively applicable to the world.
To conclude this brief journey into the philosophy of Descartes, let's make a brief list of the central points of the legacy of his thought. The first is that with Descartes, modern philosophy is born, founded on the centrality of human reason. The second is the contribution that Descartes made to the scientific revolution, defining a universal method based on mathematical language and arguing that nature acts in a purely mechanical way. The third is innatism, or the presence of innate ideas, from which reason is able to produce universally valid knowledge.