Marcus Aurelius (167)

Dost thou not see how the handicraftsmen accommodate themselves up to a certain point to those who are not skilled in their craft- nevertheless they cling to the reason (the principles) of their art and do not endure to depart from it? Is it not strange if the architect and the physician shall have more respect to the reason (the principles) of their own arts than man to his own reason, which is common to him and the gods?

The Meditations (Book Six)http://classics.mit.edu/Antoninus/meditations.html