Ruth asked:

‘Nothing can be known.’ What is a powerful objection to this claim?

Answer by Helier Robinson

It is self-refuting. If it is true then you cannot know about it. Any self-refuting statement must be false.


Answer by Geoffrey Klempner

To expand on Helier’s answer.

There seems to be a way for the sceptic to have one’s cake and eat it, by stating, ‘Either nothing can be known, or just one thing can be known, that no other knowledge is possible.’

Now all the sceptic has to do is argue from the two alternatives:

Alternative 1. If nothing can be known then nothing can be known.

If nothing can be known then, a fortiori (from the stronger premiss) apart from the question whether anything can be known, nothing can be known. I.e. nothing else can be known.

Alternative 2. If it is possible to know that nothing else can be known then nothing else be known.

Conclusion (from or-elimination): Nothing else can be known.

Why go to all this palaver? The key, unstated, premiss in the knock-down argument against scepticism, is that the act of making an assertion implies knowledge. This might seem a rather strong claim when one looks at everyday idle talk, but even a statement like, ‘The weather is nice today,’ would be questioned if one learned that the person making the statement had not gone out of their centrally heated home or looked out of the window.

And yet, there does seem something very suspect about a self-professed sceptic, or global sceptic, making any assertions. You can’t say, ‘Nothing can be known’ if you don’t know this. It is irrelevant that a ‘case can be made’ for the truth of ‘Nothing else can be known’, because you don’t know that either.

However, there is another way to look at scepticism, not as a position or theory which one states, but rather as a performance. Whenever we want to state a belief, or a position or a theory, the sceptic steps in to silence us. Words aren’t needed for this. A wagging finger would suffice.