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The second citation of Poincaré that is of interest occurs in Leonard Nelson's System of Ethics. The decisive mistake in both Poincaré and Pirsig's use of him is a failure to understand the meaning of the term "synthetic." But this is all too common. Again, this is more thoroughly explored in The Ontology and Cosmology of Non-Euclidean Geometry. This is still actually true: models and projections can be constructed of non-Euclidean spaces, but they all involve some kinds of distortions that would not be present in true spaces of that kind. In short, non-Euclidean geometry can be conceived but cannot be visualized. The axioms of geometry do not "impose themselves upon us with such force that we couldn't conceive the contrary proposition," but a certain structure of space imposes itself upon us in "pure intuition," i.e. His answer about geometry is that the structure of space is not given to us conceptually. How could a synthetic proposition be true a priori? Of course, that is precisely the question Kant asks himself. Instead, he said that the axioms of geometry are known to be true a priori, and this is what confuses the issue. However, Kant did not make such a prediction. If the axioms of geometry are synthetic, as Kant maintained, then this theory implies a prediction, not a denial, of the possibility of non-Euclidean geometry. The existence of non-Euclidean geometry refutes Hume, not Kant, though the vulnerability of Hume's theory in this respect is as little noted as the supposed vulnerability of Kant's is as often, falsely, stated. What is then revealing is that Hume considers geometry to belong to the "relations of ideas" category: "Though there never were a circle or triangle in nature, the truths demonstrated by Euclid would for ever retain their certainty and evidence". analytic), and "matters of fact," which can (i.e. Hume, like Kant, divides all propositions into two exhaustive categories, "relations of ideas," which cannot be denied without contradiction (i.e. Or, as Hume puts it, "The contrary of every matter of fact is still possible because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so conformable to reality". In Kant's terms, because the meaning of the predicate of a synthetic proposition is not already contained in the meaning of the subject, both the affirmation and the denial of the predicate are equally possible in terms of logic alone. The mistake found here concerns the nature of synthetic a priori propositions, with the conclusion that "we couldn't conceive the contrary proposition, or build upon it a theoretic edifice." What is striking about this conclusion is that it is the precise contradiction of the definition of a synthetic proposition. Zen and the Art of Motorcycle Maintenance, p. There would be no non-Euclidian geometry. They would then impose themselves upon us with such force that we couldn't conceive the contrary proposition, or build upon it a theoretic edifice. Are they synthetic a priori, as Kant said? That is, do they exist as a fixed part of man's consciousness, independently of experience and uncreated by experience? Poincaré thought not. To solve the problem of what is mathematical truth, Poincaré said, we should first ask ourselves what is the nature of geometric axioms.
#HENRI POINTCARRE PROFESSIONAL#
Although this may not seem like a serious venue for discussion of Kant, it does reflect a misunderstanding that is all too common in more professional philosophy, as may be seen in The Ontology and Cosmology of Non-Euclidean Geometry.
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The first is found in a discussion of Kant in the popular philosophical novel Zen and the Art of Motorcycle Maintenance, by Robert M. Poincaré's conventionalism is a mistake, but here I am more interested in two other citations and the kind of philosophical mistakes that they demonstrate. That kind of thing gets mentioned just in passing by people like Susan Haack (in Evidence and Inquiry, p. He is especially well known for his view that knowledge is based on conventions adopted by scientists and mathematicians, not on objectively determined features of reality. His interests also ranged into philosophical issues, in the philosophy of science and mathematics and even in the relation of science to morality. Jules Henri Poincaré (1854-1912) was one of the greatest mathematicians of his era and is sometimes said to deserve co-credit with Einstein for the discovery of Relativity. Two Philosophical Mistakes in Poincaré Two Philosophical Mistakes in Poincaré