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

That is why I can’t in any way approve of those MEDDLESOME and RESTLESS characters who, without being called by BIRTH or by FORTUNE to the management of public affairs, are yet forever thinking up some new reform! If I thought this present work contained the SLIGHTEST ground for suspecting me of such FOLLY, I would SHRINK from allowing it to be published! My plan has NEVER gone beyond trying to reform my own thoughts and to build on a foundation that is ALL MY OWN. If I’m pleased enough with my work to present you with this sketch of it, it’s not because I would advise anyone to imitate it. Those on whom GOD has bestowed more of his favours than he has on me will PERHAPS have higher aims; but I’m afraid that this project of mine may be too bold for many people! The mere decision to rid myself all the opinions I have hitherto accepted isn’t an example that everyone ought to follow! The world is mostly made up of two types of minds for whom it is QUITE unsuitable. (1) There are those who, believing themselves cleverer than they are, can’t help rushing to judgment and can’t muster the patience to direct all their thoughts in an ORDERLY manner. So that if they ONCE took the liberty of doubting the principles they have accepted and leaving the common path, they would NEVER be able to stay on the straighter path that they ought to take, AND would REMAIN lost ALL their LIVES. (2) And there are those who are reasonable enough, or modest enough, to THINK that they can’t distinguish true from false as well as some other people by whom they can be taught. THESE should be content to follow the opinions of those others rather than to seek better opinions themselves.

All that I have, up to this moment, accepted as possessed of the highest truth and certainty, I received either from or through the senses. I observed, however, that these sometimes misled us; and it is the part of prudence not to place absolute confidence in that by which we have even once been deceived.

Bueno es saber algo de las costumbres de otros pueblos, para juzgar las del propio con mejor acierto, y no creer que todo lo que sea contrario a nuestras modas es ridículo y opuesto a la razón, como suelen hacer los que no han visto nada.