ABSTRACT
A collective belief has the immense advantage of uniting in a single bundle all the manifold individual desires, of making a nation act as a single individual would act. The slowness of the evolution of beliefs constitutes one of the most essential facts of history, and at the same time one of the facts the least explained by historians. Psychology alone permits to determine its causes. The refraction of ideas, that is to say, the deformation of concepts according to race, age, sex, education, is one of the least explored questions of psychology. Ancestral concepts are the heritage of the race, the legacy of ancestors immediate or far removed, an unconscious legacy bestowed at birth, and which determines the principal motives of conduct. If the acquired concepts do sometimes succeed in contending with the ancestral concepts it is that the latter have been neutralised or annulled by contrary heritages, as happens, in crosses between members of different races.
