erm, well, ah, almost nothing. Say it again. OWWWW!
OK, so before I can start talking about what faith is good for, I guess I need to define what it is, or at least how I'm using it in this context. Let's have a look at dictionary.com:
1. confidence or trust in a person or thing: faith in another's ability.
2. belief that is not based on proof: He had faith that the hypothesis would be substantiated by fact.
3. belief in God or in the doctrines or teachings of religion: the firm faith of the Pilgrims.
4. belief in anything, as a code of ethics, standards of merit, etc.: to be of the same faith with someone concerning honesty.
5. a system of religious belief: the Christian faith; the Jewish faith.
6. the obligation of loyalty or fidelity to a person, promise, engagement, etc.: Failure to appear would be breaking faith.
7. the observance of this obligation; fidelity to one's promise, oath, allegiance, etc.: He was the only one who proved his faith during our recent troubles.
8. Christian Theology. the trust in God and in His promises as made through Christ and the Scriptures by which humans are justified or saved. —Idiom
9. in faith, in truth; indeed: In faith, he is a fine lad.
I'm talking about definitions 2, 3, 5 and 8, with maybe a smattering of 4.
I might even add a definition of my own that I think is probably omitted because it's supposed to be impolite to question someone's faith.
10. Belief that is in spite of the, often overwhelming, evidence to the contrary. AKA the "LALALALA, I'm not listening." defence.
There are plenty of arguments for it, not many of them valid. What follows is my attempt at deconstructing the major ones I've heard. Note that I’m not refuting arguments for why people have faith (check out Pascal Boyer’s Religion Explained for that), I’m refuting arguments that people give for their faith; these two are not the same thing.