Do-Gooder

Yes, defending altruism's legitimate existence remains a difficult argument in which to engage. Undoubtedly, those arguments illuminating the intangible gains of helping another seem nothing-but-true. That is, it is a difficult task to say altruism exists, and we humans are not perpetually selfish.

Perhaps you are thinking, "this is a worn-out argument." Is it, though? This philosophical, psychological, evolutionary-scientific argument would basically "decide" whether or not the human species (and other animal species, for that matter) are ultimately selfish, or are granted the freedom to break loose from hedonism should we so desire.

So, what about Neuroscience's evidence on the matter? Engaging in an action that benefits another while detracting from oneself apparently activates the Mesolimbic system of the brain: the brain's basic reward system. This is the same system implicated in drug-taking behavior. So is this evidence of our selfishness? I don't think so. Engaging in an action merely to benefit yourself from it - and doing a good deed "just because" and benefiting from a sense of wellbeing as pleasant side effect are two different things entirely. Just because one benefits does not mean they acted simply to gain a reward of sorts.

Perhaps a new argument (perhaps not, I don't know) is that from the view of one who believes altruism does not exist. Does this individual (the non-believer) gain from an altruistic act? Maybe if they aren't directly contemplating the fact that they will gain from such an event, then they do. Then, as a consequence of a thoughtful act, they are bestowed with good will (or endorphins or dopamine). This unearths several questions:
1.) What was the motivation, then? Are we posing altruism as some "unconscious" act, where our body secretly knows (that sneaky body of ours) that we will revel in some warmthy goodness if we do some good deed, so it urges us along to do it without informing our "conscious mind." Wow. That is kind of hardcore for an element that is not physiologically needed for survival. Okay, but if we aim in bettering another through the sacrifice of our own self without knowledge of its benefits, is that not an ultimately selfless act? If we are not consciously aimed toward a "prize," aren't we by definition engaging in altruism?
So follow me...
2.) If one knowingly aims to aid another because they expect to feel good as a consequence, do they actually garner a warm emotional-soulful sensation? Does the warmth only follow one's intention to receive nothing in return for the giving of one's self? Instead, does one feel ashamed for having done something "good" only to ultimately better their own being?

I think it boils down to freedom. We may engage in a selfless act. It may be rewarding. Ultimately, though, we don't have to. Sometimes we give. Sometimes that is enough.