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4 ideas
17185 | Mathematics deals with the essences and properties of forms [Spinoza] |
17222 | The sum of its angles follows from a triangle's nature [Spinoza] |
17197 | The idea of a triangle involves truths about it, so those are part of its essence [Spinoza] |
18392 | Classes have cardinalities, so their members must all be treated as units [Armstrong] |