The Existence of God
Daniel von Wachter
Issues involved
•How does “God” refer?
•What is God supposed tobe like?
•What makes theistic beliefrational? (basic belief vsarguments)
•What makes (e.g.)Christian commitmentrational?
•How, in general, doesone 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 likethat.
•God is omniscient.
•God is perfectly free and good.
•Different concepts of “God” need to bedistinguished. So “Is God a person?” is not aninteresting question.
Arguments for atheism
•Argument from evil (the evil in the worldmakes it less probable that there is a God)
•Argument from hiddenness
Arguments for theism
•Cosmologicalargument (existence ofthe universe)
•Teleologicalarguments (life; laws;fine tuning)
•Humans as evidence
•Miracles as evidence
•Religious experience
•Ontological arguments(existence, ornecessary existence,belong to the idea ofGod)
Arguments for atheism
•Argument from evil (the evil in the world makes itmore probable that there is no God); see Howard-Snyder, ed., The Evidential Argument from Evil.
•Argument from divine hiddenness (If there is aGod, why does he not make his existence moreobvious?); see Howard-Snyder, Daniel, and PaulK. Moser, eds. 2002. 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 universeis fine tuned so-and-so; there are humanbeings, conscious, ...; ...
How to evaluate evidence? (cont)
•The relation of x leading us to expect y; y iswhat we should (might...) expect given x; xmaking y more probable. E.g. there havingbeen an earthquake in the sea leads us toexpect makes a tidal wave (of kind W).
•Swinburne’s example: do the gardenerfingerprints on the safe (e) make it morelikely 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)) (predictivepower)
•Should we expect e anyway? (P(e|k))
•How probable is h independently of e? (Priorprobability of h; P(h|k)) This depends onsimplicity 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 thathave equal power to explain e?
•This applies also for hypotheses of metaphysicsbut it may give us only comparative probabilities.
Evidence for and against theism
•The existence of ouruniverse
•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 ofevidence for theism
•The question about all thisis whether and how muchit supports theism oratheism; not whether thereis a German proof.
The argument from fine tuning
•... as an example of an argument for theism.
•Had at the Big Bang been certain things slightlydifferently our universe would have developedvery differently in certain ways.
•The universe is fine tuned for embodied life. Forlife there needs to be space with chunks of matter,governed by a certain kind of laws, chunks not toobig and not too small, with not too much and nottoo little space between them.
•Example: the strength of the BB: the kineticenergy of cosmic matter corresponds quite exactlyto the gravitational energy.
Argument from fine tuning (cont)
•Example: Had the nuclear weak force beenappreciably stronger then the Big Bag would haveburned all hydrogen to helium. There could thenbe neither water nor long-lived stabile stars.Making it appreciably weaker would again havedestroyed the hydrogen: the neutrons formed atearly times would not have decayed into protons.
•More examples: John Leslie 1989 Universes; MJRees Just Six Numbers.
Argument from fine tuning (cont)
•The intuition is that the evidence cries out for anexplanation and that theism offers the bestexplanation. (E.g. Paley’s watch) But can wemake this more rigorous?
•What does a ‘need of being explained’ consist in?
•For any fact we can either accept it as brute fact orelse accept some explanation.
•We should accept it as brute fact only if there is noexplanation available that is powerful and simple.
How much does the fine tuningsupport 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 oneentity, 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 Godto bring about.)
•P(e|h.k) is not very high, but not very low.
•Therefore, the universe’s apparent being finetuned for life supports the hypothesis that there isa God. P(h|e.k)>P(h|k)