Though it was my original intention to deliver only two lectures, I have been moved by several reasons to add a supplementary one. In the first place, I notice with regret that I have been compelled by pressure of time to leave untouched in my earlier lectures, or to treat very inadequately, several important points in my theme; there is, in particular, the very important question of the nature of the soul. In the second place, I have been convinced by the many contradictory press-notices during the last few days that many of my incomplete observations have been misunderstood or misinterpreted. And, thirdly, it seemed advisable to give a brief and clear summary of the whole subject in this farewell lecture, to take a short survey of the past, present, and future of the theory of evolution, and especially its relation to the three great questions of personal immortality, the freedom of the will, and the personality of God. I must claim the reader's patience and indulgence even to a greater extent than in the previous chapters, as the subject is one of the most difficult and obscure that the human mind approaches. I have dealt at length in my recent works, _The Riddle of the Universe_ and _The Wonders of Life_, with the controversial questions of biology that I treat cursorily here. But I would like to put before you now, in a general survey, the powerful arguments that modern science employs against the prevailing superstition in regard to evolution, and to show that the Monistic system throws a clear light on the great questions of God and the world, the soul and life. In the previous chapters I have tried to give a general idea of the present state of the theory of evolution and its victorious struggle with the older legend of creation. We have seen that even the most advanced organism, man, was not brought into being by a creative act, but gradually developed from a long series of mammal ancestors. We also saw that the most man-like mammals, the anthropoid apes, have substantially the same structure as man, and that the evolution of the latter from the former can now be regarded as a fully established hypothesis, or, rather, an historical fact. But in this study we had in view mainly the structure of the body and its various organs. We touched very briefly on the evolution of the human mind, or the immaterial soul that dwells in the body for a time, according to a venerable tradition. To-day we turn chiefly to the development of the soul, and consider whether man's mental development is controlled by the same natural laws as that of his body, and whether it also is inseparably bound up with that of the rest of the mammals.