This book deals with the source and aim of Human Progress.

If we wish social life not to become stationary and stagnant, we should give free scope to all individuality and originality, no matter how eccentric they may seem to us. We should allow free play to all opinions, doctrines, and expressions of human thought, no matter how absurd and contagious the superstitions may appear to us. New ideas, ideals, and beliefs should not be persecuted but should rather be left for discussion and criticism, because we should not assume that we are in possession of the whole truth, and that no further advance is possible. We may learn from other people who look at the world from a different angle, and thus may be able to see things in a different light which may either add to the truth which we already possess, or may even transform it by some new additional element or principle which at first may appear to us as bizarre and paradoxical... The manifestation of the apparently false opinion keeps thought awake; it constantly challenges us, making us review again and again our established truths, and contributes to an ever deeper realization of what has been gained by severe thought and hard labor. The freedom of the seemingly false opinion and our tolerance of it and our willingness to meet with it in the open help test the validity of truth while keeping alive the critical sense which is the main spring of all advancement of human thought and is the vital point, the very soul, of all human progress. In a certain sense it may be said that it is the function of the false to keep the truth alive. The suppression of the freedom of thought or the liberty of individual expression, whether in speech or in press, is the crushing of all true human progress. Thus science, Sociology, Social Psychology, all go to confirm the same central attitude towards the free manifestation of individuality in the life existence of a well-ordered, progressive commonwealth...