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Single Idea 12949

[filed under theme 13. Knowledge Criteria / D. Scepticism / 1. Scepticism ]

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.

Gist of Idea

Light takes time to reach us, so objects we see may now not exist

Source

Gottfried Leibniz (New Essays on Human Understanding [1704], 2.09)

Book Ref

Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.135

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.

The 33 ideas with the same theme [general doubts about the possibility of knowledge]:

411 If we succeed in speaking the truth, we cannot know we have done it [Xenophanes]
1545 Protagoras was the first to claim that there are two contradictory arguments about everything [Protagoras, by Diog. Laertius]
578 Cratylus decided speech was hopeless, and his only expression was the movement of a finger [Cratylus, by Aristotle]
577 Democritus says there is either no truth, or it is concealed from us [Democritus, by Aristotle]
20895 We actually know nothing, and opinions are mere flux [Democritus]
1528 We in fact know nothing, but we each restructure our reality with beliefs [Democritus]
492 It is obviously impossible to understand the reality of each thing [Democritus]
515 We know nothing in reality; for truth lies in an abyss [Democritus]
13792 There can't be any knowledge if things are constantly changing [Plato]
3061 Anaxarchus said that he was not even sure that he knew nothing [Anaxarchus, by Diog. Laertius]
6593 The Pyrrhonians attacked the dogmas of professors, not ordinary people [Pyrrho, by Fogelin]
4549 Epicurus denied knowledge in order to retain morality or hedonism as the highest values [Nietzsche on Epicurus]
1870 The basis of scepticism is the claim that every proposition has an equal opposing proposition [Sext.Empiricus]
1819 Scepticism has two dogmas: that nothing is definable, and every argument has an opposite argument [Diog. Laertius]
6260 Sceptics say there is truth, but no means of making or testing lasting judgements [Montaigne]
6347 Descartes can't begin again, because sceptics doubt cognitive processes as well as beliefs [Pollock/Cruz on Descartes]
2251 Even if my body and objects are imaginary, there may be simpler things which are true [Descartes]
12949 Light takes time to reach us, so objects we see may now not exist [Leibniz]
2238 Reason can never show that experiences are connected to external objects [Hume]
2242 Mitigated scepticism draws attention to the limitations of human reason, and encourages modesty [Hume]
4708 Kant thought he had refuted scepticism, but his critics say he is a sceptic, for rejecting reality [O'Grady on Kant]
14872 Our knowledge is illogical, because it rests on false identities between things [Nietzsche]
14879 The most extreme scepticism is when you even give up logic [Nietzsche]
6591 Doubts can't exist if they are inexpressible or unanswerable [Wittgenstein]
8593 Maybe billions of changeless years have elapsed since my last meal [Shoemaker]
13314 Protagoras says arguments on both sides are always equal [Kim, by Seneca]
530 There are two contradictory arguments about everything [Kim]
8722 No one knows anything, and no one is ever justified or reasonable [Unger]
7413 Without confidence in our beliefs, how should we actually live? [Tuck]
3594 Scepticism just reveals our limited ability to explain things [Williams,M]
6071 Scepticism about reality is possible because existence isn't part of appearances [McGinn]
19501 We assess error against background knowledge, but that is just what radical scepticism challenges [Pritchard,D]
12401 A toper who spies in the distance... [Sommers,W]