Russell’s writing is as clear as a window pane, and he uses copious everyday examples to illustrate every point. He starts off, for example, by considering his desk. He is asking whether we can really know anything with any certainty, and shows that even the desk in front of him is not as apparently solid and unchanging as it at first appears. Its shape changes depending on viewpoint, its colour shifts with the light, its texture is smooth when viewed from a distance but rugged when viewed through a microscope, and so on.

He uses this to lead into Descartes system of systematic doubt, i.e. not believing anything unless he was quite certain it was true. Doing this, it becomes clear, makes us reevaluate many of the things that common sense tells us are true and real. How do we know, for example, that the sun will rise tomorrow? We may say that it has risen every morning in the past, or we may give an answer based on the laws of motion. But in either case, we have to ask ourselves whether we truly know that something will happen simply because it has happened that way countless times in the past. Russell give the wonderful example of a chicken receiving food from a man every day of its life, until at last the man wrings its neck. The chicken may have been reasonable to expect food based on past occurrences, but “more refined views as to the uniformity of nature would have been useful to the chicken.”

Russell uses similar vivid examples and clear language to explain various philosophical concepts and ways of thinking, such as induction (which starts from the particular to arrive at other particulars or general principles) and deduction (which goes from general principles to other general principles or to the particular). He gives quick portraits of the views of philosophers such as Kant and Hegel, before finishing with a wonderful summary of the value of studying philosophy, in which he admits that philosophy still has large unanswered questions, but states that as a virtue rather than a flaw:

The value of philosophy is, in fact, to be sought largely in its very uncertainty. The man who has no tincture of philosophy goes through life imprisoned in the prejudices derived from common sense … Philosophy, though unable to tell us with certainty what is the true answer to the doubts which it raises, is able to suggest many possibilities which enlarge our thoughts and free them from the tyranny of custom.

I like this idea of valuing the questions rather than the answers, of embracing uncertainty as superior to false certainty. The final paragraph is beautiful:

Philosophy is to be studied … because these questions enlarge our conception of what is possible, enrich our intellectual imagination, and diminish the dogmatic assurance which closes the mind against speculation; but above all because, through the greatness of the universe which philosophy contemplates, the mind also is rendered great, and becomes capable of that union with the universe which constitutes its highest good.

The trouble is that, in the end, it comes down to that anyway. The calm logic proceeds slowly from step to step, and I am with him all the way, until he makes a big leap, which is that scientific theories of evolution cannot explain the development of human rational thought. Because the process of reasoning is so completely different from anything we can find in the animal world, he argues, it cannot come from that world. Therefore it must come from outside, i.e. from God. On this point his whole argument rests – because each human brain is an intrusion of the supernatural into the world of Nature, so other intrusions are plausible too. He sees miracles in this way – not as breaking the rules of nature, but as sporadic intrusions by God, after which the rules of nature continue to work with the new situation.

In the framework he has constructed, most of his arguments are logical. But his framework is based on a logical leap I don’t think is justified. It’s very hard to understand a lot of evolutionary theory intuitively. I can’t imagine basic organisms evolving into giraffes, or a fish coming out of the water, developing the ability to breathe and becoming an amphibian. But I can accept that over countless millions of years, countless tiny, incremental changes could add up to huge, incomprehensible changes. The development of reason doesn’t seem to me so different from anything else that we have to give it a supernatural cause.

Another problem with the book is that all of the miracles are Christian. This is Lewis’s belief system, so it’s understandable that he would be interested in proving the viability of the virgin birth more than anything else. But he is completely dismissive of other religions, without making any attempt to explain why. If Christian miracles are possible, then are Hindu or animist ones possible. Presumably not, because Christians say there can only be one God.

But the reason for believing the Christian miracles specifically comes down to an absurd criterion called “our innate sense of the fitness of things.” The last few chapters are devoted to trying to prove that the Christian miracles meet this bizarrely vague standard of “fitness.” Lewis does not seem to consider that his own assumptions of how the universe should be are unlikely to be the same as someone else’s. People like him, the “we” of his definition, white male Oxford dons, might agree with his “innate sense of the fitness of things”, although many, clearly, would not. As for people all over the world of different origins, different religions, different social status, etc etc, surely they would have their own sense of what is “fit”? And, perhaps, they would have their own ways of describing the supernatural, and different religions would form, each as valid in its generalities and false in its details as Christianity.

I am willing to believe that miracles could happen, but not because of this book. C.S. Lewis raises some interesting ideas, but after all the long philosophical arguments it comes down once again to a question of belief.