THE GOD THEOREM
I got the idea for this book when someone once asked me, "how can a mathematician be a Christian? After all a mathematician only believes what he can prove while a Christian has to believe certain things by faith?" I began to realise that mathematics and theology are similar in many ways. They are different to the sciences in that neither use the scientific method, involving experimentation. In both cases there's a set of basic assumptions. In a particular area of mathematics there's a set of axioms. In theology we call it a creed. In both cases we build up a collection of consequences, which in mathematics are called 'theorems'.
Of course there are differences. The arguments in theology are not as logically rigorous as in mathematics and no mathematician, so far as I know, has become a martyr for his or her mathematical beliefs. But axioms, that is, unprovable assumptions, exist in everyday life. I develop a set of fundamental axioms for life that all sane people accept as true, yet they cannot be proved.
(1) I exist. [Cogito ergo sum. The evidence for this seems to be compelling but that couldn't be called a proof in the sense of logic.]
(2) The external world exists. [All I experience directly are what goes on in my brain. I believe that what I see and hear actually exist, though hallucinations do occur. What if everything is an hallucination and the world is no bigger than my brain?]
(3) You exist. [You, as a physical object, exist by axiom (2), but what I mean here is that you have consciousness. Could it not be possible that you, and everyone else are clever robots and that I alone have consciousness?]
(4) Memory is continuous. [I wake up each morning remembering a good deal of what has happened on previous days, but I can't prove that what I remember of yesterday is what actually happened.]
(5) Logic is valid. [The basic tenets of logic seem obvious but I can't prove them using logic. That would involve a circular argument.]
After some philosophical discussion along these lines, where I assert that the axiom that God exists, as well as the alternative axiom that God does not exist, are both unprovable, though I can't prove that). In other words I assert that logically both are valid beliefs and we are logically free to be a theist or an atheist. I mention that in higher mathematics there are certain statements that can actually be proved to be unprovable!
I then go on to discuss various aspects of Christian belief along similar lines to C.S. Lewis in his Mere Christianity. Later chapters include Creation, Miracles, Christmas, The Death and Resurrection of Jesus, Food and Sex, Pain and Death, Heaven and Hell, Loneliness, Angels, The Quantum God and Love.
In an appendix I give a perfectly valid logical proof (one without circular references) that God exists. But since it can be adapted to prove that God does not exist, this is merely a logical curiosity.