The childish objection against scepticism that it contradicts itself may have way in the scepticism of Pyrrhon, because such scepticism is dogmatic, but fails if brought against the scepticism of the New Academy.

The system of Pyrrhus, because it does not doubt itself, because it admits a certainty somewhere, contradicts itself. The thought of Genesidemus, which is not a system doubts itself even.

Again when we say as a reproach to the sceptics that their system is selfcontradictory, we forget that ours also is in contradiction with itself. «All things are uncertain» says the sceptic; «then» it is replied, «it is uncertain that all things are uncertain».

«Reason can find truth» we assert. But how do we know that reason can find truth? By a critique of reason. And with what do we criticize reason? With reason. Then reason proves itself? Why cannot, in the same way, doubt prove itself.

Plato’s criticism of Protagoras is based upon an equal error. Plato pretends to confound Protagoras by asserting that, since the sophist holds that each man’s sensation is his truth it follows that the system of Protagoras is true only for Protagoras and therefore untrue [...]

Scepticism, to begin, is not a system of philosophy. lt is not a theory of things but a theory of knowledge. The argument, so often brought against it, of a self‑contradiction is false, because a theory of knowledge cannot contradict itself.

A system of philosophy may imply a contradiction, i.e. a contradiction between it and reason. But reason cannot be in contradiction with reason: neither certitude with certitude nor doubt with doubt. The usual argument against scepticism is childish and ill-conceived.

Can there be a critique of scepticism? Can there be a Critique of reason?

But does scepticism bear upon reason, or does it bear upon the work of reason or the data of the senses? Not, obviously, upon reason, for it is by reason that its work of destruction is done.

«Reason», say the sceptics, «is powerless to attain the truth». As a means it is insufficient. But it proves itself insufficient.

The argument of Pascal, that things being related in all senses, to know one completely we must know all, is at the same time false and true.

In considering scepticism we have to consider 2 things: what scepticism means by truth, by thing, and what scepticism means by knowledge. For the proposition of Sc[epticism] is: «we cannot ever know anything».

By thing that is required to know cannot mean things as we see them, for these we know beyond all doubt. (It cannot be the simple laws of things for these are of the same kind and are obtained by observation).

It must mean the essence of things.