You cannot take apart what I said and then refute it piece by piece. This would be like me taking Bible quotes and saying "Peter says to be gentle, but sometimes you have to be firm. Paul says to love one another, but sometimes you have to be harsh. Jesus says if someone asks for your coat then give them your shirt to, but sometimes this is not possible if you have obligations in life (e.g., having that shirt so you can go to work and feed your family)". Using your technique, just about anyone could refute the entirety of the Bible with little effort. When I said "The sources of our morality: nature, nurture, reason, desires, and needs," I meant all of those, and probably even more sources than that.
Nurture doesn't cut it, because where did the teachers learn it?
Within the context of the other source I gave, I believe it does. You think to trap me in an infinite regression paradox, but it will not work. Your question as to where the teachers learned it is based on a false assumption: that the teachers couldn't have thought it up themselves. Maybe they learnt it partly from nature (as someone prone towards alcoholism "learns" something--a physical tendency--partly from nature). Or maybe they learnt it partly from nurture, maybe someone said or did something to them at some point which profoundly effected their beliefs. Or maybe they just came up with it partly on their own, using reason. Probably none of these sources will be the only place that they got their belief or action.
I would hope that even a Christian could agree with what I am saying in this regard: for who here believes that they are unbiased, uneffected by life, false thinking, etc.? We all are pulled this way and that. The difference is that the Christian would posit a true morality that somehow permeates our being and can keep us on the right path, normally attributing the method of delivery to nature (since most people in history have never read the Bible or heard the Gospel, morality must be given to us in at least one other way
than the written or spoken Judeo-Christian message); on the other hand, I don't agree with this assessment.
Desires doesn't cut it either, because people abstain from what they desire, and this is the same as for 'nature'.
I'm not sure why you are attributing to the sources I gave a deterministic quality. When did I ever say that someone MUST follow nature, or MUST follow desire? I think quite the opposite: that we constantly live in a jumble of intellectual contradictions, and if it were not for our ability to form a collection of thoughts (schema) we'd go mad from all the conflicting data. Now, whether the schema is close to reality/truth is a different matter entirely... but it keeps us sane, at least.
A man might lay down his life to save a stranger. He gains nothing out of it (in a naturalistic sense).
While I don't really have to respond to this last bit, since I didn't actually say what you seemed to think that I said, I would just note that I'm sure naturalistscould come up with many reasons that a man might give his life for a stranger. For example, maybe he thinks the stranger has a better chance than he does of reproducing and helping humanity to prosper. Maybe he thinks the man might serve a higher calling (maybe the guy who gets saved is plainly a doctor of some type, while the life-saver is a stock boy at toys r us). Or maybe the person's own morality (learning through whatever means) dictates to him that it is better to try and save someone else's life, even if there is a chance to fail, than to stand idly by and do nothing. I'm partial to the last answer, but it could be any number of answers, besides some God-given direction.