If the Sun were to explode we could not know of it until eight minutes later,

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If the Sun were to explode we could not know of it until eight minutes later, because that is how long it takes for light to travel from the Sun to Earth. So for eight minutes we would see an unexploded Sun, while the real sun would be exploded. It follows that we do not see the real Sun. But everything we see must be later than reality, because of the time it takes light to travel from reality to our eyes, so nothing we see is real. Can this be true?

We do not see the sun as it is at the moment of our seeing; but it certainly does not follow from this that we do not see the real sun.

There are all kinds of delays, transformations and distortions of sensual evidence. This has led some philosophers (notably Descartes) to doubt whether sensual evidence can be relied upon to give an accurate 'picture' of how the world is. Descartes even went so far as to doubt whether things outside of him really existed at all. But the fact that I can doubt something is different from evidence for it not being real. Accordingly, Descartes did not argue that the general unreliability of sensual evidence had, as an implication, that what was sensed was not real.

So, in your example, that the sun has ceased to be in the meantime (and therefore is no longer a real thing) is a problem about the reliability of our sensible knowledge in the present, but not a problem about the reality of what is sensed.

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