I have dealt mainly with two salient points—the problem of the source of a star’s energy, and the change of mass which must occur if there is any evolution of faint stars from bright stars. I have shown how these _appear_ to meet in the _hypothesis_ of the annihilation of matter. I _do not hold this as a secure conclusion_. I _hesitate even to advocate it as probable_, because there are many details which seem to me to throw _considerable doubt_ on it, and I have formed a strong impression that there must be _some essential point which has not yet been grasped_. I _simply_ tell it you as the _clue_ which at the moment we are _trying_ to follow up—_not knowing whether it is false scent or true_. I should have liked to have closed these lectures by leading up to some great climax. But perhaps it is more in accordance with the true conditions of scientific progress that they should _fizzle out_ with a glimpse of the _obscurity_ which marks the frontiers of present knowledge. I do not apologize for the [p127] _lameness_ of the conclusion, _for it is not a conclusion_. I _wish I could feel confident that it is even a beginning_. This great climax, to which Dr. Eddington was unable to lead up, is what the layman is looking for. We know quite well what the nature of that great climax would be: it would be a statement of fact which related the destiny of each individual to the destiny of the universe. That is the kind of truth which is found in revelation. It is the kind of truth which men would like to find in science. But it is the kind of truth which science does not afford. The difficulty is deeper than the provisional character of scientific hypothesis; it is not due merely to the inability of the scientist to say that his conclusion is absolutely secure. The layman in search of a dogma upon which to organize his destiny might be willing to grant that the conclusions of science to-day are as yet provisional. What he tends to misunderstand is that even if the conclusions were guaranteed by all investigators now and for all time to come, those conclusions would still fail to provide him with a conception of the world of which the great climax was a prophecy of the fate of creation in terms of his hopes and fears.