Some people think that "humanist" is just the new word for "atheist." That is not quite true. Humanists, at least the secular variety, are all atheists, but not all atheists are humanists.
Humanism can trace its western roots back to Thales, an Ionian Greek (c. 624-546 BCE), who contradicted the religion of Mythos that said the gods gave mankind all its knowledge. Thales said that mankind was capable of Logos, the discovery of knowledge through scientific inquiry and logic. In effect, he said that knowledge and ethics were humanos -- human centred.
Humanists, and yes, the word is correctly capitalized because it is an organized movement, have a well developed set of ethical codes laid out in the Amsterdam declarations of 1952, and 2002 and generally quoted or referenced in most Humanist organizations across Canada.
These ethical codes are available online (IHEU Amsterdam declarations) and they add up to being good without gods.
Sometimes people ask whether Humanism is not just another religion. In fact, it exhibits many of the characteristics of religion: social interaction, mutual support, fellowship, charitable work, and ethical guidelines. Humanism, however, lacks two characteristics of religion: it does not demand that members swear to obey supernatural beings and it does not bring dogma top down upon its members.
Humanists do look at various philosophers for ideas. However, it does not see them as people to follow blindly or worship. These philosophers have simply elucidated Humanist ideals in clear ways. They are philosophers that Humanists hold up as having useful ideas.
For example, when Humanists look at Epicurus' three paths to pleasure: learning, knowing, senses, Humanists can see that he left one source of pleasure out. All these actions stimulate dopamine in our brain, thus giving us that little pleasure jolt of which he speaks. Modern neuro-scientists have confirmed that human beings also get the same kind of jolt from helping others -- an action Epicurus ignored.
Were Epicurus alive today, Humanists would feel no compunction about bringing this to his attention and would hardly expect him to try hurling a thunderbolt. They might expect to lose any ensuing debate, because of Epicurus' intellect, not any superhuman attributes.
Secular Humanists look at philosophers' ideas more as touchstones than as moral imperatives. Humanists will often encounter an idea and judge it by a built in sense of right and wrong. In other words, while Humanists may respect one person's opinion over that of the general population, they do not see it as infallible.
That built in sense of right and wrong comes from the evolved dopamine reaction, balanced by tribalism, governed by reason. In other words, will the action allow the Humanist to help another through some logical exercise of effort without becoming vulnerable?
Humanists do have moral values and ethics and a definable philosophy and social structure just like any other social group. Those ethics and values go beyond the simple atheist statement that supernatural beings do not exist. Humanists are not interested in attacking other religions or philosophies. When religious people attempt to force their religious practices on others and Humanists in public forums, Humanists will oppose that action, but not the religious beliefs of the proponents.
In short, Humanists are here. It is a definable group with definable ethics and philosophies. Humanism is a philosophy that may be atheist based, but the word Humanist does not replace the term atheist.