If I find some reason for doubt in each of my beliefs, that will be enough to reject all of them. - René Descartes

"In everyday life we must often act without delay, it is a most certain truth that when it is not in our power to discern the truest opinions, we must follow the most probable." (Discourse III, AT VI: 25/CSM I: 123)

[Descartes discusses a traveler lost in a forest to illustrate this. The traveler is lost, and he does not know how to get out of the woods. Descartes’ advice is that the traveler should pick a route, even if it is uncertain, and resolutely stick to it:

"Keep walking as straight as he can in one direction, never changing it for slight reasons even if mere chance made him choose it in the first place; for in this way, even if he does not go exactly where he wishes, he will at least end up in a place where he is likely to be better off than in the middle of a forest." (Ibid.)]

C'est quasi le même de conserver avec ceux des autres siècles que de voyager.

But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search