Revolutions occur which nothing can prevent. It is an inevitable evil, and Comte gives a striking psychological reason for it. Our mind is too weak and our life too short for us ever to form a positive idea of a social system other than the one in which we were born and in which we live. It is from this one that, willingly or unwillingly, we draw the elements of our political and social ideas. Even men of a utopian turn of mind do not escape this necessity. Their dreams always reflect, at bottom, either the past, or a contemporary social state. In order that a new political system should appear, and especially for it to find access to men’s minds, the destruction of the preceeding system must be already very far advanced. Until then “even the most open minds could not perceive the characteristic nature of the new system hidden from all eyes by the spectacle of the old organisation.”[280] Hence, the lengthy processes of decomposition of worn-out _régimes_, the no less lengthy birth of new institutions, and the cruel periods of transition, full of troubles, of wars, and of revolutions. With this same cause are connected what we may call the phenomena of survival. Institutions, powers, as also doctrines, have a tendency to subsist beyond the function which the general advance of the human mind had assigned to them.[281] Conflicts then take place which it is beyond anybody’s power to prevent: happy is he who can make them shorter and less acute! The solution only comes with time when the vanquished ideas fall into “disuse.” The combat never ceases except from the lack of combatants. All this in no way excludes the possibility for man to exercise a beneficent or a detrimental action. To understand is not always to justify. It is true that a comprehensive view of history disposes us to be indulgent, because it brings out the close solidarity of all the social elements of the same period. The responsibilities being shared, and so to speak diffused, appear to be less serious for each individual. Nevertheless this philosophy allows praise and blame for the past, and active intervention in social phenomena for the present. But this intervention will only produce the desired results if it rests upon social science. The positive polity does not propose to direct the human race towards an arbitrarily selected end. It knows that humanity is moved by its own impulse, “according to a law no less necessary, although more modifiable than that of gravitation.”[282] It is only a question for politics to facilitate this advance by throwing light upon it. It is a very difficult thing to undergo the action of a law without understanding it, or to submit to it with a full knowledge of the case. It remains in man’s power to soften and to shorten crises, as soon as he grasps their reasons and foresees the issue. He will not pretend to govern the phenomena, but only to modify their spontaneous development. “This demands that he should know their laws.”[283]