The unseen line
Every action that people take can be placed along a hidden, impossible to ascertain criterion:
to what extent is the action taken with the actual benefit of others, and to what extent is it done with a the interests of the person committing in mind.
altruism as a concept would be some extreme point along this spectrum. something that is done completely without any thought of personal benefit, even an indirect one.
some would say that all motivation derives from the self and consequently cannot be truly altruistic, though the personal benefit may be unclear, or likley to materialize only in the very long run.
another popular argument is the selfish gene theory, whereby any apparent act of self sacrifice by one organism to another is predicated on benefitting those who share genetic material (such as offspring) , thus indirectly benefitting the particular bloodline , of which the perpetrator is a member. acts of apparent altruism between genetically distant members is less likely, and can be explained as a general benefit to the species in some way.
the realist school sees all actions as derived from man's desire to increase his benefitting factors or at least protecting them from being reduced. therefore altruism is absolutely impossible.
but here is the thing, almost everybody is capable of empathy, and most also have a sympathetic reaction to pain and suffering. it could be argued that we experience such an emotional reaction as a way to anticipate others of our kind and improve our chances of survival and propagation. on the other hand, most people also experience sympathetic reaction to animals, trees, innanimate objects and even fictional charachters. clearly, anticipating any of these can not benefit us as organisms. but still we can't help ourselves.
it is this sympathy and these objects that prove, in my opinion that there are more occasions of altruism than we could guess.
many people do good things to others. they sacrifice little or a lot of their resources and even rarely, their lives, to others. while it is easy to argue that they are doing so out of some hidden motivation, it could be just this uncontrolled sypathetic reaction, that drives them and possibly ovverides considerations of their self interest. many dramatic instances of saving lives, for example, happen with very little time to calculate all the angles of benefit versus risk.
another explanation to altruism cpuld be that the assumption that we all function rationally and in the best of our interests is totaly false. the human mind is a massively complex thing. it oparates far beyond the very basic drives that our primitive ancestors had. we integrate massive amounts of axperience and interact with others in sophisticated and diverse ways. somewhere along this complexity, many of our ideas, and drives are displaced or warped to form convictions and choices that are far from self serving and rational. while this often leads to catastrophic results, it also has a chance of causing people to behave altruistically , without any conscious anticipation for some sort of benefit.
in the end, altruism is the extreme point of spectrum, just as narcissism, and psycopathy are the other end. the displays of benevolant self-sacrifice and dedication to others are uplifting and inspiring to those that hold within them the desire to do good. even if this desire is a selfish drive, it results in normatively rasing the bar for others. somewhere along the line, people stop calculating and start giving.