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Full Idea
It seems natural to claim that light rays moving in straight lines is contingent but a priori. Scientists stipulate that they are the standard by which we measure straightness, but their appropriateness for this task is a contingent feature of the world.
Gist of Idea
Light in straight lines is contingent a priori; stipulated as straight, because they happen to be so
Source
Edwin D. Mares (A Priori [2011], 02.9)
Book Ref
Mares,Edwin: 'A Priori' [Acumen 2011], p.31
A Reaction
This resembles the metre rule in Paris. It is contingent that something is a certain way, so we make being that way a conventional truth, which can therefore be known via the convention, rather than via the contingent fact.
| 12736 | If we understand God and his choices, we have a priori knowledge of contingent truths [Leibniz, by Garber] |
| 13159 | Only God sees contingent truths a priori [Leibniz] |
| 9386 | The meter is defined necessarily, but the stick being one meter long is contingent a priori [Kripke] |
| 9385 | The very act of designating of an object with properties gives knowledge of a contingent truth [Kripke] |
| 12429 | Knowing our own existence is a priori, but not necessary [Kitcher] |
| 17703 | Light in straight lines is contingent a priori; stipulated as straight, because they happen to be so [Mares] |