Combining Texts

All the ideas for 'The Sign of Four', 'Letters to Samuel Masson' and 'Rules for the Direction of the Mind'

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3 ideas

6. Mathematics / A. Nature of Mathematics / 5. The Infinite / d. Actual infinite
I don't admit infinite numbers, and consider infinitesimals to be useful fictions [Leibniz]
     Full Idea: Notwithstanding my infinitesimal calculus, I do not admit any real infinite numbers, even though I confess that the multitude of things surpasses any finite number, or rather any number. ..I consider infinitesimal quantities to be useful fictions.
     From: Gottfried Leibniz (Letters to Samuel Masson [1716], 1716)
     A reaction: With the phrase 'useful fictions' we seem to have jumped straight into Harty Field. I'm with Leibniz on this one. The history of mathematics is a series of ingenious inventions, whenever they seem to make further exciting proofs possible.
11. Knowledge Aims / B. Certain Knowledge / 1. Certainty
In pursuing truth, anything less certain than mathematics is a waste of time [Descartes]
     Full Idea: In our search for the direct road towards truth we should busy ourselves with no object about which we cannot attain a certitude equal to that of the demonstrations of Arithmetic and Geometry.
     From: René Descartes (Rules for the Direction of the Mind [1628], Rule II), quoted by Alain Badiou - Mathematics and Philosophy: grand and little p.8
     A reaction: A beautiful statement of the way in which rationalist philosophy was founded on the model of mathematics (esp. Euclid), with all its concomitant problems. The most important concept of the last hundred years may well be fallibilist rationalism.
14. Science / C. Induction / 1. Induction
If you eliminate the impossible, the truth will remain, even if it is weird [Conan Doyle]
     Full Idea: When you have eliminated the impossible, whatever remains, however improbable, must be the truth.
     From: Arthur Conan Doyle (The Sign of Four [1890], Ch. 6)
     A reaction: A beautiful statement, by Sherlock Holmes, of Eliminative Induction. It is obviously not true, of course. Many options may still face you after you have eliminated what is actually impossible.