Reflecting upon it continually, I was forced to recognise that the problem was composed of a series of other problems, which I should have to study separately. This I did for a period of twenty years, presenting the results of my researches in a succession of volumes. One of the first was devoted to the study of the psychological laws of the evolution of peoples. Having shown that the historic races--that is, the races formed by the hazards of history--finally acquired psychological characteristics as stable as their anatomical characteristics, I attempted to explain how a people transforms its institutions, its languages, and its arts. I explained in the same work why it was that individual personalities, under the influence of sudden variations of environment, might be entirely disaggregated. But besides the fixed collectivities formed by the peoples, there are mobile and transitory collectivities known as crowds. Now these crowds or mobs, by the aid of which the great movements of history are accomplished, have characteristics absolutely different from those of the individuals who compose them. What are these characteristics, and how are they evolved? This new problem was examined in The Psychology of the Crowd. Only after these studies did I begin to perceive certain influences which had escaped me. But this was not all. Among the most important factors of history one was preponderant--the factor of beliefs. How are these beliefs born, and are they really rational and voluntary, as was long taught? Are they not rather unconscious and independent of all reason? A difficult question, which I dealt with in my last book, Opinions and Beliefs. So long as psychology regards beliefs as voluntary and rational they will remain inexplicable. Having proved that they are usually irrational and always involuntary, I was able to propound the solution of this important problem; how it was that beliefs which no reason could justify were admitted without difficulty by the most enlightened spirits of all ages. The solution of the historical difficulties which had so long been sought was thenceforth obvious. I arrived at the conclusion that beside the rational logic which conditions thought, and was formerly regarded as our sole guide, there exist very different forms of logic: affective logic, collective logic, and mystic logic, which usually overrule the reason and engender the generative impulses of our conduct. This fact well established, it seemed to me evident that if a great number of historical events are often uncomprehended, it is because we seek to interpret them in the light of a logic which in reality has very little influence upon their genesis.