The Existence of God Daniel von Wachter

Issues involved How does “God” refer? What is God supposed to be like? What makes theistic belief rational? (basic belief vs arguments) What makes (e.g.) Christian commitment rational? How, in general, does one belief support (being evidence) another belief? Support for atheism. Support for theism.

What is God supposed to be like? God is a person, i.e. he acts and has a mental life. God doesn’t need a body. God is omnipotent. He can do everything just like that. God is omniscient. God is perfectly free and good. Different concepts of “God” need to be distinguished. So “Is God a person?” is not an interesting question.

Arguments for atheism Argument from evil (the evil in the world makes it less probable that there is a God) Argument from hiddenness

Arguments for theism Cosmological argument (existence of the universe) Teleological arguments (life; laws; fine tuning) Humans as evidence Miracles as evidence Religious experience Ontological arguments (existence, or necessary existence, belong to the idea of God)

Arguments for atheism Argument from evil (the evil in the world makes it more probable that there is no God); see Howard- Snyder, ed., The Evidential Argument from Evil. Argument from divine hiddenness (If there is a God, why does he not make his existence more obvious?); see Howard-Snyder, Daniel, and Paul K. Moser, eds Divine Hiddenness: Cambridge UP.

How to evaluate evidence? The hypothesis, h: here is a God The evidence, e1, e2,...: There is a universe; the laws L govern the universe; the universe is fine tuned so-and-so; there are human beings, conscious,...;...

How to evaluate evidence? (cont) The relation of x leading us to expect y; y is what we should (might...) expect given x; x making y more probable. E.g. there having been an earthquake in the sea leads us to expect makes a tidal wave (of kind W). Swinburne’s example: do the gardener fingerprints on the safe (e) make it more likely that (h) he was the thief?

How to evaluate evidence? (cont) How probable is h on e? (P(h|e.k)) That depends on: Does h lead us to expect e? (P(e|h.k)) (predictive power) Should we expect e anyway? (P(e|k)) How probable is h independently of e? (Prior probability of h; P(h|k)) This depends on simplicity and fit with background knowledge. P(h|e.k) = { P(e|h.k) / P(e|k) } × P(h|k) (Bayes) How do we judge between two hypothesis that have equal power to explain e? This applies also for hypotheses of metaphysics but it may give us only comparative probabilities.

Evidence for and against theism The existence of our universe Life on earth Beauty Laws of nature Fine tuning Our minds Religious experience Miracles Details of some religion (e.g. Jesus’ message The evil in the world The actual amount of evidence for theism The question about all this is whether and how much it supports theism or atheism; not whether there is a German proof.

The argument from fine tuning... as an example of an argument for theism. Had at the Big Bang been certain things slightly differently our universe would have developed very differently in certain ways. The universe is fine tuned for embodied life. For life there needs to be space with chunks of matter, governed by a certain kind of laws, chunks not too big and not too small, with not too much and not too little space between them. Example: the strength of the BB: the kinetic energy of cosmic matter corresponds quite exactly to the gravitational energy.

Argument from fine tuning (cont) Example: Had the nuclear weak force been appreciably stronger then the Big Bag would have burned all hydrogen to helium. There could then be neither water nor long-lived stabile stars. Making it appreciably weaker would again have destroyed the hydrogen: the neutrons formed at early times would not have decayed into protons. More examples: John Leslie 1989 Universes; MJ Rees Just Six Numbers.

Argument from fine tuning (cont) The intuition is that the evidence cries out for an explanation and that theism offers the best explanation. (E.g. Paley’s watch) But can we make this more rigorous? What does a ‘need of being explained’ consist in? For any fact we can either accept it as brute fact or else accept some explanation. We should accept it as brute fact only if there is no explanation available that is powerful and simple.

How much does the fine tuning support theism? P(h|e.k) = { P(e|h.k) / P(e|k) } × P(h|k) P(h|k) is high because theism is simple: just one entity, simple properties,... P(e|k) is low: e is not likely to occur anyway (whether or not h) P(e|h.k) ? (Consider what you would expect a God to bring about.) P(e|h.k) is not very high, but not very low. Therefore, the universe’s apparent being fine tuned for life supports the hypothesis that there is a God. P(h|e.k)>P(h|k)