Descartes' Rationalism: Reason, Method, and Mechanistic Worldview

Context: René Descartes and 17th-Century Philosophy

René Descartes, a prominent figure of the seventeenth century, is considered the father of modern philosophy. A great mathematician, he is known for inventing analytic geometry. He founded the influential school of continental rationalism, characterized by:

• Confidence in Reason

  Reason, as opposed to sensory experience, is the primary source of truth. It is infallible and capable of uncovering innate truths independently of sensory experience. From these foundational ideas, more complex truths are derived through deduction. There is a parallel between the world and reason, as both operate according to logical laws.

• Mechanistic Worldview

  The world is viewed as a machine governed by laws. This mechanistic perspective leads to determinism, where everything is determined by prior states. As Laplace famously stated, an intelligence knowing the state of all particles could infer the past and future. However, this raises the problem of free will. Rationalists address this by positing two realities: one governed by physical laws and another by spiritual laws, leading to a dualism of soul and body, similar to Plato's philosophy.

• Search for a New Method

  Rationalists seek a method based on mathematics, attempting to emulate the exact sciences in philosophy. They start with self-evident axioms and derive theorems from them. Descartes employed methodical doubt to find foundational truths, as demonstrated in his famous "Discourse on the Method."

• Subjectivity and Knowledge

  Humans know their thoughts directly but perceive the external world indirectly through ideas. Therefore, certainty about the external world's composition is unattainable, as its existence is not self-evident and can be doubted.

Modern science, forged during the Renaissance (fifteenth and sixteenth centuries), strongly influenced rationalism. A paradigm shift occurred, leading to a mechanistic worldview where the universe is a machine governed by laws. This shift prompted a search for a mathematical method in philosophy, echoing the spirit of Pythagoreanism.