The belief that politics can be scientific must inevitably produce tyrannies. Politics cannot be a science, because in politics theory and practice cannot be separated, and the sciences depend upon their separation. Empirical politics must be kept in bounds by democratic institutions, which leave it up to the subjects of the experiment to say whether it shall be tried, and to stop it if they dislike it, because, in politics, there is a distinction, unknown to science, between Truth and Justice.