For me, the moral difficulties lie in the continual pressure brought to bear on my friends and immediate family, pressure which is not directed against me personally but which at the same time is all around me.

Profound insights arise only in debate, with a possibility of counterargument, only when there is a possibility of expressing not only correct ideas but also dubious ideas.

You can't sit on two chairs at once.

In 1947 I defended my thesis on nuclear physics, and in 1948 I was included in a group of research scientists whose task was to develop nuclear weapons.

For me, the moral difficulties lie in the continual pressure brought to bear on my friends and immediate family, pressure which is not directed against me personally but which at the same time is all around me.

Intellectual freedom is the only guarantee of a scientific - democratic approach to politics, economic development, and culture.

My present work concerns the problems connected with the theory of elementary particles, the theory of gravitation and cosmology and I shall be glad if I can manage to make some contribution to these important branches of science.