When1: 1618
When2: 1649
Who: René Descartes [Descartes, René]
What: mathematician/philosopher
Where: France
works\ Musical Compendium [1618]; Rules for the Direction of the Mind [1628]; Treatise on Man [1629]; Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences [1637]; World [1634]; Geometry [1637]; Optics [1637]; Meteorology [1637]; Meditations on First Philosophy [1641]; Principles of Philosophy [1644]; Passions of the Soul [1649]
Detail: He lived 1596 to 1650, was Catholic, and was "father of modern philosophy". In mathematics, he studied analytic geometry, slope, rectangular coordinates, Cartesian products, absolute value, sign rule, undetermined-coefficients principle, and logarithmic spirals.
Epistemology
God's purposes cannot explain anything, because people cannot know those purposes.
Senses and opinions cannot be true, because they can change and often deceive. People cannot know if they are asleep or awake and so they can be incorrect about image or thought {dreaming argument}. An evil demon {malin genie} or outside agent can perpetually deceive people. Because people can always perceive deceptive things, people cannot be certain about personal experiences or actions or about mathematical propositions and tautologies. Doubting everything is suspending judgment. One can doubt existence of all physical objects. However, the act of doubting implies consciousness, so people cannot doubt their existence as thinking faculties or consciousnesses with thoughts {method of doubt, Descartes} {cogito argument}. People cannot doubt doubting, so "cogito ergo sum" or "I think therefore I am".
However, ability to doubt that thing possesses some feature does not prove that thing can exist without feature.
Doubting, affirming, denying, understanding, willing, hating, imagining, and feeling are consciousness parts. Consciousness or soul essence is thinking, which happens even in deep sleep.
The method of doubting demonstrates a fact about truth: If a statement is as clear and distinct as the truth that the doubter exists, the statement must be true. Such statements must be as clear as tautologies and as distinct as exact meanings. Such truths {innate idea} are true by themselves and do not require deduction from other truths. Therefore, people can know clear and distinct statements. They can know them by reason, which comes from God. Mind passively receives cause mental effects. However, because body can cause unclear ideas, mind has to actively find clear and distinct truths.
Facts and theories do not and cannot lead to truth. Rather, analysis or induction methods should reach one and only one basic and certain principle. From that principle, deduction and synthesis can explain everything. All knowledge can connect in logical systems.
Cause must have more reality than effects. People have an idea of perfect being. However, people are finite and not perfect and so cannot themselves conceive of perfect things. Only a perfect being can put ideas of perfect things into consciousness. Therefore, God must exist, and "God exists" is clear and distinct.
Because God is perfect and so is truthful, God never creates people so they always have error. People can therefore believe in knowledge that is clear and distinct. Most truths have clarity and distinctness and do not need deduction. For example, mathematical truths are clear and distinct. Deduction only corroborates them. People can believe bodies exist, though mind knows only their extension, number, flexibility, and motion. Qualitative judgments and sense perceptions are mental signs, are not clear and distinct, and so are not truths.
Total motion in cause equals that in effect {conservation, motion} {motion conservation}.
Ethics
Rational thinking about clear and distinct ideas results in proper willing and action. Will can judge clear and distinct ideas in only one way and so is not free in those cases. Error in willing and action can arise when ideas are not clear and distinct and will is free in those cases. Sin arises from will's incorrect choice in unclear or indistinct cases.
Feelings and desires are mental disturbances caused by body. Only humans have feelings, because only they combine mind and body. Feelings and desires come from fundamental feelings: wonder or admiration, love, hate, desire or want, pleasure or joy, and pain or sadness. The mind's duty is to control body effects on mind.
Metaphysics
There must be a first cause for all things and especially for the whole. Reality has God, souls, and matter. The mental, non-material, and spiritual world, which has mental activities or consciousness, is entirely separate from physical world. Only one mental level exists. Mental or soul substance {res cogitans} does not extend in space and is indivisible. Physical substance {res extensa, Descartes} extends and is divisible. Material objects in motion fill space and follow deterministic motion laws. The physical world is the same everywhere. Living things are complex mechanical objects with no animating force. Math and physics can apply to body {iatrophysicism} (Giovanni Alfonso Borelli).
Mind
Soul and body are two independent things but interact. Psychological properties differ from physical properties {attributive dualism}, and psychological descriptions cannot be physiological descriptions.
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Date Modified: 2022.0224