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 and after 1964 when I began to concern myself with the biological issues, and particularly from 1967 onwards, the extent of the problems over which I felt uneasy increased to such a point that in 1968 I felt a compelling urge to make my views public.

International affairs must be completely permeated with scientific methodology and a democratic spirit, with a fearless weighing of all facts, views, and theories, with maximum publicity of ultimate and intermediate goals, and with a consistency of principles.

A country which does not respect the rights of its own citizens will not respect the rights of its neighbours

Nothing threatens freedom of the personality and the meaning of life like war, poverty, terror. But there are also indirect and only slightly more remote dangers. One of these is the stupefaction of man (the "gray mass," to use the cynical term of bourgeois prognosticators) by mass culture with its intentional or commercially motivated lowering of intellectual level and content, with its stress on entertainment or utilitarianism, and with its carefully protective censorship.

Our country, like every modern state, needs profound democratic reforms. It needs political and ideological pluralism, a mixed economy and protection of human rights and the opening up of society.