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411 | If we succeed in speaking the truth, we cannot know we have done it [Xenophanes] |
Full Idea: No man has seen certain truth, and no man will ever know about the gods and other things I mentioned; for if he succeeds in saying what is fully true, he himself is unaware of it; opinion is fixed by fate on all things. | |
From: Xenophanes (fragments/reports [c.530 BCE], B34), quoted by Sextus Empiricus - Against the Professors (six books) 7.49.4 |
12949 | Light takes time to reach us, so objects we see may now not exist [Leibniz] |
Full Idea: Since rays of light need time - however little - to reach us, it is possible that the object should be destroyed during the interval and no longer exist when the light reaches the eye. | |
From: Gottfried Leibniz (New Essays on Human Understanding [1704], 2.09) | |
A reaction: This is the well know 'time lag' argument. Leibniz is no sceptic, but he can hardly fail to accept the truth of this problem. It seems self-evident that stars we observe may no longer exist, although special relativity confuses that issue. |