I have pointed out a distinction between biological and social, or psychological, heredity. But there is one instance in which the two agree. This is that we can only understand a thing by its history. We may catalogue the existing peculiarities of an animal form with no other material than that of the organism before us, but thoroughly to understand it we must know its history. Similarly, existing institutions may have their justification in the present, but the causes of their existence lie buried in the past. A king may to-day be honoured on account of his personal worth, but the reason why there is a king to be honoured carries us back to that state of culture in which the primitive priest and magic worker inspires fear and awe. When we ring bells to call people to church we perpetuate the fact that our ancestors rang them to drive away evil spirits. We wear black at a funeral because our primitive ancestors wished to hide themselves from the dead man's ghost. We strew flowers on a grave because food and other things were once buried with the dead so that their spirits might accompany the dead to the next world. In short, with all human customs we are forced, if we wish to know the reason for their present existence, to seek it in the ideas that have dominated the minds of previous generations.[4] [4] "The tyranny exercised unconsciously on men's minds is the only real tyranny, because it cannot be fought against. Tiberius, Ghengis Khan, and Napoleon were assuredly redoubtable tyrants, but from the depths of their graves Moses, Buddha, Jesus, and Mahomet exerted on the human soul a far profounder tyranny. A conspiracy may overthrow a tyrant, but what can it avail against a firmly established belief? In its violent struggle with Roman Catholicism it is the French Revolution that has been vanquished, and this in spite of the fact that the sympathy of the crowd was apparently on its side, and in spite of recourse to destructive measures as pitiless as those of the Inquisition. The only real tyrants that humanity has known have always been the memories of its dead, or the illusions it has forged for itself" (Gustave Le Bon, _The Crowd_, p. 153).