An action, to have moral worth, must be done from duty.

Look closely. The beautiful may be small.

If an offender has committed murder, he must die. In this case, no possible substitute can satisfy justice. For there is no parallel between death and even the most miserable life, so that there is no equality of crime and retribution unless the perpetrator is judicially put to death.

Our knowledge springs from two fundamental sources of the mind; the first is the capacity of receiving representations (receptivity for impressions), the second is the power of knowing an object through these representations (spontaneity [in the production] of concepts).

It is precisely in knowing its limits that philosophy consists.

We find that the more a cultivated reason devotes itself to the aim of enjoying life and happiness, the further does man get away from true contentment.

Man's greatest concern is to know how he shall properly fill his place in the universe and correctly understand what he must be in order to be a man.