There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible.

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.

I think; therefore I am.

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.

But possibly I am something more than I suppose myself to be.

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.

If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.