What would it take to determine the correct degree selfishness versus selflessness?

Will work on the answer. Being able to predict the future (especially beyond death) seems the main thing.

Why am I really vegan?

Is it because:
To me there is no such thing as not acting in one's own self interest. I don't really believe in the existence of altruism. Yet I definitely act in a manner that appears more altruistic than average. I do so because I see farther into a possible future. And the farther one goes into some undermined hazy future, the more selfish reasons there are to care about the happiness of other beings.

Of course if the people around us are happy, that generally increases our own happiness provided they aren't people who get happy by hurting others.

I live as if I'll live forever in some form. Over such a long term unknown scope, there becomes more reason to just go ahead and keep others happy.

What if when we die we return to some collective conscious along with all other creatures? What if we still to some extent have our indivduality while at the same time being connected with all these others. We kill a massive number of animals for food, what if they aren't real happy about that and harbor a grudge against us into the afterlife while being psychicly(sp) connected to us?

Silly but well, I don't know. And it's easy to be vegan. So this seemingly altruistic act is really not necessarily altruistic.

Or is it just empathy? Just that I try to understand the point of view of others. And thus I literally feel their pain to an extent and simply can't stand then to cause them pain? Is that it? Something so straightforward, not quite so silly.

Is it pride? That I've identified certain behaviors as monsterous and decided I will not act in certain ways simply because I want to play this Game well?