Combining Texts

Ideas for 'On What Grounds What', 'The Ethics' and 'Theory of Knowledge (2nd ed 1977)'

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4 ideas

6. Mathematics / A. Nature of Mathematics / 1. Mathematics
Mathematics deals with the essences and properties of forms [Spinoza]
     Full Idea: Mathematics does not deal with ends, but with the essences and properties of forms (figures), …and has placed before us another rule of truth.
     From: Baruch de Spinoza (The Ethics [1675], IApp)
     A reaction: Just what I need - a nice clear assertion of essentialism in mathematics. Many say maths is all necessary, so essence is irrelevant, but I say explanations occur in mathematics, and that points to essentialism.
6. Mathematics / A. Nature of Mathematics / 2. Geometry
The sum of its angles follows from a triangle's nature [Spinoza]
     Full Idea: It follows from the nature of a triangle that its three angles are equal to two right angles.
     From: Baruch de Spinoza (The Ethics [1675], IV Pr 57)
     A reaction: This is the essentialist view of mathematics, which I take to be connected to explanation, which I take to be connected to the direction of explanation.
The idea of a triangle involves truths about it, so those are part of its essence [Spinoza]
     Full Idea: The idea of the triangle must involve the affirmation that its three angles are equal to two right angles. Therefore this affirmation pertains to the essence of the idea of a triangle.
     From: Baruch de Spinoza (The Ethics [1675], II Pr 49)
     A reaction: This seems to say that the essence is what is inescapable when you think of something. Does that mean that brandy is part of the essence of Napoleon? (Presumably not) Spinoza is ignoring the direction of explanation here.
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / a. For mathematical platonism
If 'there are red roses' implies 'there are roses', then 'there are prime numbers' implies 'there are numbers' [Schaffer,J]
     Full Idea: We can automatically infer 'there are roses' from 'there are red roses' (with no shift in the meaning of 'roses'). Likewise one can automatically infer 'there are numbers' from 'there are prime numbers'.
     From: Jonathan Schaffer (On What Grounds What [2009], 2.1)
     A reaction: He similarly observes that the atheist's 'God is a fictional character' implies 'there are fictional characters'. Schaffer is not committing to a strong platonism with his claim - merely that the existence of numbers is hardly worth disputing.