I prefer rules of thumb.
This essay offers a few tips to help with various philosophical problems. First off is a simple test to refute a claim:
Let's begin with a heuristic that is easy to use, but quite fertile. The word ‘the’ is the most common word in English. A locution of the form ‘… the X …’ – what philosophers call a definite description – typically comes with an assumption that there is exactly one X. We might be able to challenge that assumption, in two ways: perhaps there is more than one X; perhaps there are no Xs. So the heuristic here is to see the word ‘the’ in neon lights, as it were – by italicising it, underlining it, or otherwise mentally highlighting it – and to try each challenge.and goes on to show how effective it can be with various problems. Eventually leading to this nice example of the short-comings of philosophy. Given the proof: 1)If God exists he would have created the best of all possible worlds 2)This isn't the best of all possible worlds, therefore God doesn't exist
... perhaps God exists, but didn't create anything. Yet one might insist that he must have, perhaps regarding that as a part of the meaning of ‘God’. This brings us to the second premise. Again, note the contrast: our world, as opposed to other worlds. This prompts a different response: God did not create our world, but he created the best of all possible worlds (instead). This suggests that the argument is invalid: we can imagine premises 1 and 2 being true, without being committed to the conclusion. Or imagine that God did create the best of all possible worlds; and the second best; and the third best… Eventually, we get to our world, which is way down the list, but he created it nonetheless – perhaps because there is still a net balance of good over evil. Again, this suggests that the argument is invalid – only ‘suggests’, mind; perhaps it is impossible for one God to create multiple worlds, for reasons given by David Lewis in On the Plurality of Worlds (1986). It presupposes that God faces a world limit.Worth a read
Where does this leave us? Well, we did not manage to prove the existence of God, nor prove his non-existence. (I hope you are not too disappointed!) But that’s par for the course in philosophy – it rarely proves anythingconclusively. Instead, I hope I have given you some sense of what philosophical reasoning is like, and how that reasoning can be stimulated and enhanced by the use of various heuristics. Along the way, we saw some instances of what followed from what (or not), exposed some sophisms, spotted some fallacies, and policed some of our reasoning.