In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.
I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.
Thoughts without content are empty, intuitions without concepts are blind.
Happiness is not an ideal of reason, but of imagination.
All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason.
Reason has always existed, but not always in a reasonable form.
In order to protect ourselves we must live like doctors and be continually treating ourselves with reason.
Reason must be our last judge and guide in everything.
All rational action is in the first place individual action. Only the individual thinks. Only the individual reasons. Only the individual acts.
Never get angry. Never make a threat. Reason with people.
It is right that we should stand by and act on our principles; but not right to hold them in obstinate blindness.
There is nothing without a reason.
Let us calculate.
A man has free choice to the extent that he is rational.
Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.
A wise man proportions his belief to the evidence.
Things which are equal to the same thing are also equal to one another.
Everything must justify its existence before the judgment seat of Reason, or give up existence.
It will never be possible by pure reason to arrive at some absolute truth.
