This old chestnut comes up time and time again, but I haven’t seen a better set of answers than are given here by Stephen Law in the draft introduction to his new book.
His seven key definitions are as follows:
First, humanists are either atheists or at least agnostic. They are sceptical about the claim that there exists a god or gods. They are also sceptical about angels, demons and other such supernatural beings.
Secondly, humanists believe that this life is the only life we have. We are not reincarnated. Nor is there any heaven or hell to which we go after we die.
Third, Humanists reject both the claims that there cannot be moral value without God, and that we will not be, or are unlikely to be, good without God and religion to guide us. Humanists deny that our moral sense was placed in us by God, and generally favour a naturalistic, evolutionary account of how our moral intuitions have developed. Humanists reject moral justifications rooted in religious authority and dogma. They believe our ethics should be strongly informed by study of what human beings are actually like, and of what will help them flourish in this world, rather than the next.
Fourth, humanists deny that that if our lives are to have meaning, it must be bestowed from above by God. The lives of Pablo Picasso, Florence Nightingale, Mother Theresa and Einstein were all rich, significant and meaningful, whether there is a God or not.
Fifth, humanists emphasize our individual moral autonomy. It is our individual responsibility to make our own moral judgements, rather than attempt to hand that responsibility over to some external authority – such as a religion or political leader – that will make those judgements for us. Humanists favour developing forms of moral education that emphasize this responsibility and that will equip us with the skills we will need to discharge it properly.
Sixth, Humanists believe science and reason are invaluable tools we can and should apply to all areas of life. No beliefs should be considered off-limits and protected from rational scrutiny. The humanist’s scepticism concerning gods, angels, demons, an afterlife, and so on is not a “faith position” but rather a consequence of their having subjected such beliefs to critical, scrutiny and found them severely wanting.
Seventh, humanists are secularists, in the sense that they favour an open society in which the state takes a neutral position with respect to religion, protecting the freedom of individuals to follow and espouse, or reject and criticize, both religious and atheist beliefs. While humanists will obviously oppose any attempt to coerce people into embracing religious beliefs, they are no less opposed to coercing people into embracing atheism, as happened under the communist regimes of Stalin and Mao.
So there you go: I hope that helps!