Those who are accustomed to judge by feeling do not understand the process of reasoning, because they want to comprehend at a glance and are not used to seeking for first principles. Those, on the other hand, who are accustomed to reason from first principles do not understand matters of feeling at all, because they look for first principles and are unable to comprehend at a glance.

The immortality of the soul is a matter which is of so great consequence to us and which touches us so profoundly that we must have lost all feeling to be indifferent about it.

The arithmetical machine produces effects that approach nearer to thought than all the actions of animals. But it does nothing that would enable us to attribute will to it, as to the animals.

The end point of rationality is to demonstrate the limits of rationality.

A man does not show his greatness by being at one extremity, but rather by touching both at once.

Just as I do not know where I came from, so I do not know where I am going. All I know is that when I leave this world I shall fall forever into oblivion, or into the hands of an angry God, without knowing which of the two will be my lot for eternity. Such is my state of mind, full of weakness and uncertainty. The only conclusion I can draw from all this is that I must pass my days without a thought of trying to find out what is going to happen to me.

What a chimera then is man. What a novelty! What a monster... what a contradiction, what a prodigy