Most men seldom accept even the simplest and most obvious truth if it obliges them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have taught proudly to others and which they have woven thread by thread into the fabric of their lives.
A scientist is, then, a seeker after truth. The truth is that which he reaches out for, the direction toward which his face is turned. Complete certainty is beyond his reach, though, and many questions to which he would like answers lie outside the universe of discourse of natural science.
— P.B. Medawar
One must not only have the knowledge, but also apply it. One must not only desire, but also act.