Karl Popper

Those who promise us paradise on earth never produced anything but a hell.

In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.

We must plan for freedom, and not only for security, if for no other reason than that only freedom can make security secure.

It is impossible to speak in such a way that you cannot be misunderstood.

There is no history of mankind, there are only many histories of all kinds of aspects of human life. And one of these is the history of political power. This is elevated into the history of the world.

Our knowledge can only be finite, while our ignorance must necessarily be infinite.

Piecemeal social engineering resembles physical engineering in regarding the ends as beyond the province of technology.