I accept no principles of physics which are not also accepted in mathematics.

There is nothing so strange and so unbelievable that it has not been said by one philosopher or another.

I concluded that I might take as a general rule the principle that all things which we very clearly and obviously conceive are true: only observing, however, that there is some difficulty in rightly determining the objects which we distinctly conceive.

Hence reason also demands that, since our thoughts cannot all be true because we are not wholly perfect, what truth they do possess must inevitably be found in the thoughts we have when awake, rather than in our dreams.

It is best not to go on for great quest for truth , it will only make you miserable

Because reason...is the only thing that makes us men, and distinguishes us from the beasts, I would prefer to believe that it exists, in its entirety, in each of us.

The principal effect of the passions is that they incite and persuade the mind to will the events for which they prepared the body.