Ideas from 'The World' by René Descartes [1631], by Theme Structure

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12. Knowledge Sources / B. Perception / 2. Qualities in Perception / d. Secondary qualities
Our sensation of light may not be the same as what produces the sensation
                        Full Idea: There can be a difference between our sensation of light and what is in the objects that produce that sensation in us.
                        From: René Descartes (The World [1631]), quoted by Ian Dunt - How to be a Liberal 1
                        A reaction: Note only that they 'may' differ, and that he does not assert that they are entirely different. Secondary qualities give information, and are not just mental events.
26. Natural Theory / A. Speculations on Nature / 6. Early Matter Theories / f. Ancient elements
The Hot, Cold, Wet and Dry of the philosophers need themselves to be explained
                        Full Idea: If you find it strange that in explaining these elements I do not use the qualities called Hot, Cold, Wet and Dry - as the philosophers do - I shall say to you that these qualities themselves seem to me to need explanation.
                        From: René Descartes (The World [1631], 9:25-6), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 1.3
                        A reaction: Nice. I take pushing the boundaries of explanation back (or down) to be the basic driving force of all human thought, in metaphysics as well as in physics.
27. Natural Reality / A. Classical Physics / 1. Mechanics / b. Laws of motion
Descartes said there was conservation of 'quantity of motion'
                        Full Idea: Descartes incorporated the conservation of what he called 'quantity of motion', by which he meant mass times speed.
                        From: report of René Descartes (The World [1631]) by David Papineau - Thinking about Consciousness App 2
                        A reaction: Mass times velocity is now called 'momentum'. Is this the first ever conservation law? There are now lots of them.