There is a famous story about a debate between Popper and Wittgenstein at Oxbridge. In the middle of a heated exchange, Wittgenstein is said to have grabbed a fire poker and to have begun waving it in Popper’s direction, demanding that Popper present a single ethical claim that could be said to be well founded. With the veins on Wittgenstein’s head beginning to throb, Popper is said to have calmly produced such an ethical claim: “Don’t threaten visiting professors with fire pokers.”
How much truth lies in such a philosopher’s myth is hard to say. But in any case, the story has fueled the idea that between Popper and Wittgenstein, there lies a great gulf of thought. Both men came out of Vienna, and both were heavily influenced by the logical positivists. Yet both turned their backs on this movement for different reasons. It is usually thought that Popper tried to escape the problems facing the logical positivists by invoking falsification, rather than verification, as the criterion of right belief. In contrast, the later Wittgenstein is thought to have embraced a global scepticism, rejecting as false any such claim to “right belief.”
But this caricature misses the very interesting overlap that holds between the two men’s respective epistemological theories. For both men, at the core of their theories. held that “justification” is very often, if not always, impossible. Both men rejected the very most central term in the history of epistemology (if not philosophy, more generally). Moreover, both men accepted that human knowledge was ultimately groundless. Human knowledge is not like a house built from solid ground upwards. As Popper put it:
“The foundations (of knowledge) are piers going down into a swamp from above. They do not reach a natural base, but … one resolves to be satisfied with their firmness, hoping they will carry the structure.”
And Wittgenstein went so far as to argue that our most certain beliefs could not be justified:
“If a blind man were to ask me “have you got two hands?” I should not make sure by looking. If I were to have any doubt of it, then I don’t know why I should trust my eyes. For why shouldn’t I test my eyes by looking to find out if I see two hands? What is to be tested by what?
Both men were, then, in their own different ways, anti-justificationist.
Yet the differences in their thought about anti-justificationism are particularly enlightening. For Popper, human knowledge was ultimately no more than myth-making. What made scientific knowledge so special was that the myths had not only been made, but then had also been subjected to criticism and tested against experience. Human knowledge was nothing more than trial and error. We can conjecture whatever wild myths we like. If the myths survive our trials and tests, then we are entitled to keep using them.
Wittgenstein’s anti-justificationism, on the other hand, does not present us with such a heroic picture. Instead, Wittgenstein’s anti-justificationism hinges on, well, “hinges“. According to Wittgenstein, a “hinge belief” is a practically certain belief that we deploy when we want to appraise other more hypothetical beliefs. The trouble with hinge beliefs is that if they are practically certain, then there cannot be any other beliefs about which we are more certain. Thus, we have no bedrock—no lower tier beliefs—upon which we could find support for such certainly held beliefs. For Wittgenstein, no-one can seriously doubt that there are other minds, or that the moon exists, since these are the sorts of beliefs which we deploy when we want to check whether other beliefs are correct. We cannot doubt hinge beliefs, since we doubt by using them.
I don’t want to argue here about whose views I find more appealing (cough! cough! Popper’s), but I only want to draw attention to the fact that these two philosophers, having one of the most famous philosophical rivalries of all time, shared one of their most key themes in common. Strange allies indeed!