Cartesian Philosophy: Doubt, Substance, and Mechanics
Anthropology
To achieve understanding, a universal doubt is required. Reject as false all things without evidence or uncertain validity. Descartes proposed rules known as the “methodical doubt.”
Firstly, reject information from the senses, as they can deceive. Secondly, acknowledge human reasoning errors, doubting arguments and demonstrations. Differentiate between dreams and thoughts, as there’s no clear distinction when awake or dreaming. Finally, consider the “evil genius” idea, making obvious things seem untrue.
This universal doubt isn’t skepticism but a step towards true knowledge. Descartes concludes the first truth: “I think, therefore I am.” Even if the body and surroundings are illusions, the act of thinking is undeniable. This identifies the soul, distinct from the body, as the thinking substance.
Knowledge is true if presented clearly and distinctly. Rationalists use evidence as the criterion for truth.
Cartesian Method
The initial problem is finding a guaranteed doubt, a first truth beyond doubt due to clarity and distinction. This is the starting point of learning.
The four rules are:
- Evidence: Accept only what appears clearly and distinctly.
- Analysis: Break down complex problems into simpler parts.
- Synthesis: Reassemble the simple parts to solve the problem.
- Enumeration: Review the process to ensure nothing is missed.
Thinking Substance (Res Cogitans)
The thinking self is the first substance and truth. Universal doubt leads to the existence of this reality. The fundamental attribute is thought or consciousness.
Infinite Substance (Res Infinite)
The second substance is God, infinite and divine. Descartes argues the thinking self has the idea of perfection (God), despite not being perfect.
Evidence for God’s existence:
- a) The idea of perfection and infinity. The finite self recognizes the opposite in God, who is the cause of this idea.
- b) The contingency of the self. The imperfect and finite self implies a perfect and infinite being as the cause.
Extended Substance (Res Extensa)
The third substance is material things (res extensa), with extension as the fundamental attribute, including shape, position, and movement.
Descartes’ metaphysics leads to physics. The soul is defined by thought, the body by extension.
Cartesian Physics
Descartes’ physics is mechanistic, explaining reality through efficient causality without purpose. Matter and motion are the key elements.
Motion is a change of position. The cause of motion is twofold: God as the first cause, and the interaction of matter.
Matter is pure extension, the object of geometry. Secondary qualities are not part of reality. Matter is defined by length, breadth, and depth.