Plato’s Dualism, Knowledge, and Descartes’ Doubt

Posted on Mar 24, 2025 in Philosophy and ethics

Platonic Dualism

Platonic dualism posits that man is composed of two independent entities, and neither can be reduced to the other. Its most important representative was Plato:

  1. The Body: A material reality derived from the sensible world and is mortal. It is only alive because it possesses a soul, and its death occurs when the soul separates from it. The body is considered a prison, and life is conceived as a punishment from which the individual is released only after death. The body is merely an obstacle to reaching the truth.
  2. The Soul: A spiritual reality that belongs to the world of ideas and is immortal. Due to its imperfection, it is forced to temporarily leave the ideal world to live in the world of things, locked in a body.

Source of Knowledge

There are two primary approaches to explaining the source of knowledge:

  1. Rationalists consider the reasoning process itself as the only reliable source of knowledge.
  2. Empiricists assert that all knowledge is based on information obtained through the senses.

Rationalism

René Descartes is considered the father of rationalism. He defends rationalism with these points:

  1. Geometry is the model of knowledge. From axioms and deductive logical reasoning stem a series of theorems.
  2. Rationalism distrusts information from the senses and the world. In contrast, the terms of geometry allow for deductive rigor to establish and expand knowledge.
  3. There are innate ideas in our minds. All human beings are born with them, and therefore, they do not result from knowledge of the outside world.

Empiricism

For empiricism, knowledge is based on external experience and is obtained through perception. The mind is a blank page that fills with information received by the senses. There can be no innate ideas.

The Kantian A Priori

Immanuel Kant stated, “All knowledge begins with experience, but not all knowledge proceeds from experience.”

  • Rationalism: Not all knowledge comes from experience.
  • Empiricism: Without experience, there is no knowledge.

According to Kant, the subject requires a priori conditions to capture space-time reality. This means not just how it is captured, but that it becomes payable, conforming to the conditions of sensibility.

The Cartesian Doubt

Descartes raises questions about the world and even mathematical truths. This doubt clearly covers all knowledge of the world:

  1. Doubt about reality: The senses can deceive us, leading to illusory perceptions.
  2. Doubts about mathematical truths: He initially realizes that mathematical statements are unaffected and irrefutable. He then introduces the idea of an “evil genius,” a god capable of convincing us of something even if it is false.

He then realizes there is an absolute certainty against which no doubt can be wielded: the act of thinking. “I think; therefore, I am.”

Agnosticism

Agnosticism is the position taken by those who consider that the existence of God cannot be demonstrated.

Dogmatism

Dogmatism is an opinion or belief held as certainty without a rational basis; it is accepted absolutely.