Seventeenth-Century Rationalism and Cartesian Philosophy

Rationalism in the Seventeenth Century

Rationalism in Europe developed during the seventeenth century. It emphasized order, an order analogous to mathematics, which was presented as a model of knowledge. The traditional topics covered were the world, man, and the idea of God. The most important authors included Descartes and Spinoza, among others.

Rationalism initiated modern reflections on knowledge, questioning its possible value. The core rational belief is metaphysical: truth originates from being in the thinking subject. If one thinks correctly, the emphasis is placed on what is innate rather than acquired, prioritizing a priori knowledge over a posteriori experience.

René Descartes: Father of Modern Philosophy

René Descartes, in France, is considered the father of modern philosophy. His contributions are often analyzed in two main areas: the Cartesian Method and his philosophical synthesis.

The Cartesian Method

The Method is inspired by classical logic and mathematics, providing rules for the direction of the mind:

1. Rule of Evidence or Doubt: To accept nothing as true until it is known clearly and distinctly.
2. Rule of Analysis: Reducing obscure and complicated cases to simpler ones.
3. Rule of Synthesis: Proceeding from the simplest elements to the most complex through ordered deductions.
4. Rule of Enumeration or Review: Going over the steps to ensure nothing has been omitted and that the conclusion is certain.

The essence of rationalism is demonstrated by this method: intuiting ideas that are clear and distinct, and deriving other ideas from them. The first rule, doubt, requires a critique of the principles of all knowledge. Since the senses have sometimes deceived us, we cannot trust them completely. This leads to confusion and the hypothetical supposition that an evil genius might make us doubt even mathematical truths.

Philosophical Synthesis and Innate Ideas

Descartes declared that thought consists of acts of thinking and the content of thought (ideas). He classified the contents of ideas:

Classification of Ideas

• Adventitious Ideas: Those that appear to come from the external world via sensation.
• Fictitious Ideas: Those elaborated by the mind.
• Innate Ideas: Those found within us, such as thought, existence, and the infinite.

Nativism allows Descartes to grasp the self as finite. To prove the existence of God (the infinite and perfect being), he used several arguments:

Arguments for God's Existence

1. The argument based on the Principle of Causality.
2. An argument analogous to St. Anselm's Ontological Argument.
3. An argument based on causality applied to the idea of the infinite, asserting that a perfect being must be extremely honest and good, thus ensuring that the evil genius hypothesis cannot ultimately hold true.

Substance and Dualism

The world consists of primary qualities (objective) and secondary qualities (subjective, such as color or flavor). Descartes constructed a deductive physics based on geometry. He defined Substance as that which exists in such a way that it needs nothing else to exist. Reason clearly and distinctly reveals that the body and soul are substantially separate.

The Mind-Body Interaction

Descartes explained the peculiar union between body and soul in the **pineal gland**. He theorized that "little animals" (animal spirits) scattered throughout the blood, having received external mechanical impulses, arrive at the pineal gland, which then wakes up the thinking process, leading to clear and distinct knowledge.