There are men who will kill and maim with a tranquil conscience under the influence of the words and writings of some of those who are certain that they know perfection can be reached, argued Isaiah Berlin.
Let me explain, he wrote for the New York Review of Books:
If you are truly convinced that there is some solution to all human problems, that one can conceive an ideal society which men can reach if only they do what is necessary to attain it, then you and your followers must believe that no price can be too high to pay in order to open the gates of such a paradise. Only the stupid and malevolent will resist once certain simple truths are put to them. Those who resist must be persuaded; if they cannot be persuaded, laws must be passed to restrain them; if that does not work, then coercion, if need be violence, will inevitably have to be used—if necessary, terror, slaughter.
So what is to be done to restrain the champions, sometimes very fanatical, of one or other of these values, each of whom tends to trample upon the rest, as the great tyrants of the twentieth century have trampled on the life, liberty, and human rights of millions because their eyes were fixed upon some ultimate golden future? he asked in A Message to the 21st Century:
My point is that some values clash: the ends pursued by human beings are all generated by our common nature, but their pursuit has to be to some degree controlled—liberty and the pursuit of happiness, I repeat, may not be fully compatible with each other, nor are liberty, equality, and fraternity.
So we must weigh and measure, bargain, compromise, and prevent the crushing of one form of life by its rivals….. The denial of this, the search for a single, overarching ideal because it is the one and only true one for humanity, invariably leads to coercion. …..
I am glad to note that toward the end of my long life some realization of this is beginning to dawn. Rationality, tolerance, rare enough in human history, are not despised. Liberal democracy, despite everything, despite the greatest modern scourge of fanatical, fundamentalist nationalism, is spreading. Great tyrannies are in ruins, or will be—even in China the day is not too distant.