It is contrary to reasoning to say that there is a vacuum or space in which there is absolutely nothing.

Whatever I have up till now accepted as most true and assured I have gotten either from the senses or through the senses. But from time to time I have found that the senses deceive, and it is prudent never to trust completely those who have deceived us even once.

An optimist may see a light where there is none, but why must the pessimist always run to blow it out?

Be that as it may, there is fixed in my mind a certain opinion of long standing, namely that there exists a God who is able to do anything and by whom I, such as I am, have been created. How do I know that he did not bring it about that there is no earth at all, no heavens, no extended thing, no shape, no size, no place, and yet bringing it about that all these things appear to me to exist precisely as they do now?

Neither the true nor the false roots are always real; sometimes they are imaginary; that is, while we can always imagine as many roots for each equation as I have assigned, yet there is not always a definite quantity corresponding to each root we have imagined.

Variant: When it is not in our power to follow what is true, we ought to follow what is most probable.

The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.