The distinction between the past, present and future is only a stubbornly persistent illusion.

In the middle of difficulties lie opportunities.

Everything that is really great and inspiring is created by the individual who can labor in freedom.

It is my conviction that pure mathematical construction enables us to discover the concepts and the laws connecting them, which gives us the key to the understanding of nature ... In a certain sense, therefore, I hold it true that pure thought can grasp reality, as the ancients dreamed.

The longing to behold this pre-established harmony [of phenomena and theoretical principles] is the source of the inexhaustible patience and perseverance with which Planck has devoted himself ... The state of mind which enables a man to do work of this kind is akin to that of the religious worshiper or the lover; the daily effort comes from no deliberate intention or program, but straight from the heart.

I believe that we don't need to worry about what happens after this life, as long as we do our duty here-to love and to serve.

I know that philosophically a murderer is not responsible for his crime, but I prefer not to take tea with him.