It seems like the ancients do not have a word for 'Why'. Curious that they gave birth to Philosophy in spite of this (or as Nietzsche might write, 'because of this'.) It's too bad Nietzsche did not write it. It would have been one thing he wrote I could agree with. Though I am a radical individualist, despise altruism as both unScriptural and anti-human, and am ethically an egoist (It was after all, our "selves" that Christ came to save,) I despise Nietzsche, mostly for confusing egoism with subjectivism. Those who have never even heard of Nietzsche suffer from that confusion to this day.
(If you're interested in that "it is our 'selves' that Christ came to save" statement, you might compare, Mark 8:36 and Luke 9:25 and notice what is the most important thing for a person not to lose.)
Hank
For whatever it's worth, I've found that both Kierkegaard and Nietzsche deal extensively with the interplay of forces that go into the definition of 'self'.
If you take the first lines of
Sickness Unto Death:
Man is spirit. But what is spirit? Spirit is the self. But what is the self? The self is a relation which relates itself to its own self, or it is that in the relation [which accounts for it] that the relation relates itself to its own self; the self is not the relation but [consists in the fact] that the relation relates itself to its own self. Man is a synthesis of the infinite and the finite, of the temporal and the eternal, of freedom and necessity, in short it is a synthesis. A synthesis is a relation between two factors. So regarded, man is not yet a self.
You can see that while he is attempting a 'Christian Psychological Exposition for Upbuilding and Awakening', he's dealing exclusively with the definition of the 'self'.
Nietzsche, as well, deals with the primacy of the 'self' and its interplay with senses, emotions, personal interaction, others, etc. and envisions the self as a plethora of 'wills' each attempting to dominate the others, with 'self' being ultimately defined by that will which suborns the others.
This is the Nietzsche in 'Beyond Good and Evil'. His views change, to say the least, both between books and within books.
I think my ultimate disenchantment with Ayn Rand comes from the basic response to her view as being, "So What?". I mean, of course the self is and can only be defined by the individual. What then? Mostly, we define ourselves in terms of how others see us, even if we want them to see us as being individualistic. You don't wish your will be subjected? Fine. But, working from the old saying, "Lead, Follow or Get Out of the Way", what are you working in relation to?
In other words, to be individualistic, you have to be apart from something. Even by saying you're opposed to or apart from something, you're positing a relation to something that could not exist without that thing.
Realize that typically in human affairs, I find Normative Egoism to be the case, especially where large groups are concerned. Less typical in small groups, there is almost an asymptotic point where Egoism gives way to concern. This isn't to say that Egoism is invalid. I just find it less useful where smaller or tighter groups are or may be concerned. For example democrats and republicans may hate each other, but if China invaded, those differences become negligible.
Ultimately, I see most moral codes as little more than cooperative self preservation. A great example of this is the Mayflower Compact or the Constitution. We may not agree on why murder is bad, but we know we have to outlaw it.