1. Cosmological.
The 'Chicken and Egg' question. The Cosmos must have been created by an external Agent, because every Effect must have its adequate Cause. The only adequate Cause of the Universe is God.
2. Teleological.
The 'Paley's Watch' question. The chronometer didn't just 'happen' by a foruitous concourse of atoms. It was designed for a Purpose or End (Greek /telos/) and built to a specification. Archdeacon William Paley (1743-1805) said that the existence of a watch proved the existence of a watchmaker.
3. Rational.
The 'Universal Observer' question. "Esse est Percipi" (to Be is to Be Observed: Bishop George Berkeley, 1685-1753). Science assumes the authority of Reason and the self-consistency of Reality. As Dickens creates the world of his novels in his mind, so God creates the universe in His mind, and maintains it by His observation. Continuity is pre-supposed in Logic.
Letter to the Times: "There was a young man who said 'God
Must think it exceedingly odd
That this tree which I see
Just ceases to be
When there's no-one about in the Quad.'"
Reply next day: "Dear Sir: your astonishment's odd.
I'm always about in the Quad.
This tree that you see
Shall continue to be
Observed by, yours faithfully, God."
(attributed to Mgr Ronald Knox)
4. Moral.
The 'Innate Sense of Right and Wrong' question. Man's sense of Right and Wrong is no socially-conditioned value judgement. All agree (even primitive tribespeople) that treachery, lies and lust are Wrong; mercy, truth and honour are Right (and not rationalised self-interest). A Moral Idea can only exist in a Mind; an absolute moral idea can only exist in an Absolute Mind. "So God created man in His own image...." (Genesis 1:27).
5. Ontological.
The 'Universal God-consciousness' question. Belief in God is seen as a pre- requisite for all rational enquiry. St Augustine and St Anselm said "Credo ut Intelligam" (I believe in order to understand). Sir Isaac Newton said he made all his most important discoveries upon his knees. Man's universal search for God is prima-facie evidence for the existence of the God who gave him this basic instinct.
6. Anthropological.
The 'Mind over Matter' question. Plato wrestled with this question with his theory of Forms: heavenly universals for earthly particulars. Man's moral and spiritual values, freewill, sense of justice and obligation cannot have come from Matter. Mind cannot come from Matter, nor Spirit from Flesh; therefore only a Being possessing Mind and Spirit could have made Man. Man exists; therefore God exists. The History of Religion is insufficient to explain the production of the Bible without Divine input (Special Revelation).
7. Cartesian.
The 'Cogito ergo Sum' question (I think; therefore I am): the Method of Doubt. This in fact was anticipated by St Augustine with his dictum 'I doubt; therefore Truth is'. Doubt everything, and see what happens. If an idea stands up to sustained doubt then it must be clear and distinct. In practice this means Negate the proposition to be tested, and see if you were wrong to do so (as with Truth Tables in Symbolic Logic).
Rene Descartes decided that there was no doubt at all that he existed, and therefore no doubt that God existed.
8. Christological.
The 'What do you think of Jesus' question. Consider Christ's character; fulfilled prophecy; miraculous happenings; the existence and growth of the Church in spite of persecutions; the objective New Birth experience of believers.
9. Personal.
The 'Suck it and See' approach. The proof of the pudding is in the eating; "Taste and see that the LORD is good; blessed is the man who takes refuge in him" (Psalm 34:8); "... you have tasted that the Lord is good" (1 Peter 2:2). "The Spirit himself testifies with our spirit that we are God's children" (Romans 8:16). "Anyone who comes to [God] must believe that He exists and that He rewards those who earnestly seek Him" (Hebrews 11:6). As Jesus said to Martha, "Did I not tell you that if you believed, you would see the glory of God?" (John 11:40).
Ben Crick