by Sir Karl Popper This is a great book, and an exciting book. I say so even though I happen to dis­ agree with the author in many minor points and one or two major points. Some of the minor points are merely terminological, and therefore very minor. I dislike the term 'dialectic', because of its use since Hegel and Marx; and I dislike the term 'gravitism', perhaps without a good reason. Thus I dislike the name which Professor Gal-Or has given to his theory. But the theory seems to me a great and a very beauti­ ful theory, so far as I can judge. Other minor points of disagreement are connected with Gal-Or's original and remarkable views of the great philosophers, including Spinoza and Kant. A major point of disagreement is that Gal-Or, following Einstein, is a scientific determinist, while I cannot but regard determinism as a modem super­ stition. Of course, he may be right and I may be completely mistaken. I mention these critical points rather in order to emphasize how strongly I am impressed by Professor Gal-Or's great book. Even in the very unlikely case that, wherever we disagree, he should be in the wrong and I right, even if that should be the case (which is improbable in the extreme), it would remain a great book: readable, worth reading and enlightening; with a most fascinating cosmological story of time, expansion, and gravitation.