Youssouf asked:

"Tell a man that there are 300 billion stars in the universe and he'll believe you. Tell him a bench has
wet paint on it and he'll have to touch to be sure."

What does this suggest about the way different types of knowledge are justified?

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What isit to believe that there are 300 billion stars in the universe? What's the difference between
merely considering the proposition, or supposing that there might be 300 billion stars in the universe
and really believingit? This is a question which has been intriguing me.

Your two examples involve a particular aspect of knowledge/ belief, where we acquire our beliefs via
testimony.A vast amount of the beliefs we acquire about the world arise from testimony, from what
others have told us, from what we learned in school, or from what we have read, or seen on TV etc.

It could be said that the wet paint example is a special one, because of the simple fact that paint
dries. Paint that was wet 30 minutes ago, might not be wet now. This is a piece of empirical
knowledge coming under the heading of 'stuff we know but we can't remember where we first learned
it'. Suppose instead that we were told that the bench was liable to collapse, or that it had a sign on it
saying, 'Warning: unstable'. You might take it on trust that this was the case without testing first —
especially since the only way to really test the claim is to put your full weight on the bench!

However, it remains the fact that some of the beliefs we acquire via testimony are directly testable
while others are not.

We put a great deal of faith in 'experts', but in many cases even they cannot claim to have provided
the definitive 'test' of a claim, but only given the best explanation for given data. So, for example, if an
astronomer reports the discovery of a new kind of star, it is understood that this is merely intended as
the simplest, most economical explanation of the data from observation of the heavens. You can't test
the claim by going over to the star to touch it.

However, the belief that there are billions of stars is not like that. The evidence is so overwhelming
that you would have to be a crackpot to believe otherwise. The same is true of the belief that the
earth is round. If you didseriously doubt that there were billions of stars or that the Earth was round
rather than flat then there would be no way to persuade you otherwise.

And this takes us to the issue that interests me. Since ancient times, the threat of scepticism has
been seen as a philosophical problem. Suppose an individual who doubts all the things that we
accept without question — for, example, my belief that I am awake and not being caused to 'dream'
that I am sitting at a desk, looking out of the window etc. — how could we provethat the sceptic's
hypothesis is false? The answer is, we can't. In that case, how can we justify our claim to knowledge?

It is possible to believe that the earth is flat. I once knew someone who not only sincerely believed
that the earth was flat, but had all sorts of explanations of how it is that 'the scientists' are able to pull
the wool over our eyes. What is interesting about this case is that in order to disbelievethe claim that
the earth is round, you have to believeall sorts of other things (conspiracy theories and the like).
Whereas the philosophical sceptic seriously questions whether anybelief is justified.

Geoffrey Klempner