In modern times humanism has been associated with Karl Marx and one of his teachers, Ludwig Feuerbach. The latter was an atheist who believed that it wasn't God who created man but the other way around. Since, however, this left no one to command us to do the right thing, an alternative source of morality was proposed by Feuerbach, namely, humanism.
A humanist argues, not unlike Socrates did, that ethics or morality rests on an understanding of human nature. What is right and wrong depend on what kind of beings we are. Because of our free will, we, unlike other animals, are capable of doing violence to our own nature. But we ought to choose to follow it, instead.
As it happens, Marx, who took quite a few of his ideas from Feuerbach, held a collectivist conception of human nature. "The human essence," he said in his famous essay "On the Jewish Question," "is the true collectivity of man."
So the desire to find ethical guidance from an understanding of human nature came to the advocacy of an out and out collectivist morality. If, as Marx held, we are specie-beings, so that our flourishing or development in life must be achieved together, in concert, if individuality is a myth and collectivity the norm, then humanistic ethics and politics will, accordingly, be collectivist.
The two most emphatic humanists of this kind were Karl Marx and Auguste Comte. They both thought that only a secular understanding of human affairs made sense but they also embraced a conception of human nature that left little room for the fact of human individuality. As a result most humanists have been socialists, communists, or something close to these and have found capitalism anathema to human nature.
This is very unfortunate because although flourishing among others is a crucial attribute of human life, the essential individuality of human beings cannot be denied. Even engaging in arguments testifies to this, let alone the incredible diversity evident throughout history and the globe, especially involving human creativity. Indeed, it is arguable that the most genuine humanism is individualism.
The issue of humanism is vita for several reasons. Although fundamentalist religions will likely always be part of human life, there is also a growing awareness that ethics and morality, including our sense of justice, must gain a footing apart from theology or religion. The reason is that faith is ineffable, ultimately. It is too personal, too subjective, and thus it tends toward schism rather than harmony. Whereas the humanist idea that an understanding of human nature, based on science and ordinary human reason, holds out promise.
Ethical ideals, if they are part of the human world, need to be ascertained in such a way that everyone who but consults his or her reason can grasp them. Such a replacement of a more religious approach to ethics, now that the world has become so small, is a welcome idea.
However, if humanism remains wedded to collectivism, it will turn out to be a false and dangerous alternative to faith based ethics.