Give back to the world at least what you've received.

God may be subtle, but he isn't plain mean.

The sole function of education...[is] to open the way to thinking and knowing, and the school, as the outstanding organ for the people's education, must serve that end exclusively.

If one tries to navigate unknown waters one runs the risk of shipwreck

I believe that whatever we do or live for has its causality; it is good, however, that we cannot see through to it.

The contemplation of this world beckoned as a liberation (...)The road to this paradise was not as comfortable and alluring as the road to the religious paradise; but it has shown itself reliable, and I have never regretted having chosen it.

I know that it is a hopeless undertaking to debate about fundamental value judgements. For instance, if someone approves, as a goal, the extirpation of the human race from the earth, one cannot refute such a viewpoint on rational grounds. But if there is agreement on certain goals and values, one can argue rationally about the means by which these objectives may be obtained.