THE gradual passage of the race of man from the condition of "beasts that reason not" to that of "persons of understanding and reason" has been an immensely long and a very painful one. It is not yet complete--is far, indeed, from being so--even amongst the most favoured classes of the most highly civilized peoples of to-day. Just as our bodily evolution and adaptation to present conditions is incomplete and exhibits what Metchnikoff has called "disharmonies"--that is, retentions of ancestral structures now not only useless, but even positively injurious--so does the mental condition attained by civilized man (if we do not limit our observation to exceptional instances) exhibit a retention--by means of records and accepted teaching--of beliefs and tendencies which were among the first products of the blundering efforts of human reason, and have caused atrocious suffering to millions of human beings in the long process of mental development. At one time the whole race lived in a world of delusions and fantastic beliefs--the outcome of false or defective observation rather than of false logic. These false conclusions as to many subjects were inevitable as soon as man began to reason at all. It was the necessary and injurious accompaniment of the growing habit of "reasoning" by which the more fortunate races have eventually been brought, step by step, to correct conclusions and a dominant position at the present day. The progress from the almost universal prevalence of an enormous system of preposterous false beliefs or conclusions onward to the triumph of sound knowledge has not only taken an immense period of time, but left whole races of men and large sections of the population--even in those races which have produced individuals remarkable for their power of discovering the truth--still subject to the early erroneous conceptions of natural processes and of man's relation to them.