Dubium sapientiae initium (Doubt is the origin of wisdom).

Dubium sapientiae initium. (Doubt is the origin of wisdom.)

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.

...we ought also to consider as false all that is doubtful.

... moral certainty is certainty which is sufficient to regulate our behaviour, or which measures up to the certainty we have on matters relating to the conduct of life which we never normally doubt, though we know that it is possible, absolutely speaking, that they may be false.