From the Humanists UK:
Throughout recorded history there have been non-religious people who have believed that this life is the only life we have, that the universe is a natural phenomenon with no supernatural side, and that we can live ethical and fulfilling lives on the basis of reason and humanity. They have trusted to the scientific method, evidence, and reason to discover truths about the universe and have placed human welfare and happiness at the centre of their ethical decision making.
Today, people who share these beliefs and values are called humanists and this combination of attitudes is called Humanism. Many millions of people in Britain share this way of living and of looking at the world, but many of them have not heard the word ‘humanist’ and don’t realise that it describes what they believe.
It is one of the main purposes of Humanists UK to increase public awareness of what Humanism is, and to let the many millions of non-religious people in this country know that, far from being somehow deficient in their values, they have an outlook on life which is coherent and widely-shared, which has inspired some of the world’s greatest artists, writers, scientists, philosophers and social reformers, and which has a millenia-long tradition in both the western and eastern worlds.
We also hope to give greater confidence to people whose beliefs are humanist by offering resources here and elsewhere that can develop their knowledge of humanist approaches to some of the big ethical, philosophical and existential questions in life.
Roughly speaking, the word humanist has come to mean someone who:
trusts to the scientific method when it comes to understanding how the universe works and rejects the idea of the supernatural (and is therefore an atheist or agnostic)
makes their ethical decisions based on reason, empathy, and a concern for human beings and other sentient animals
believes that, in the absence of an afterlife and any discernible purpose to the universe, human beings can act to give their own lives meaning by seeking happiness in this life and helping others to do the same.
However, definitions abound and there are longer and shorter versions. The fullest definition to have a measure of international agreement is contained in the 2002 Amsterdam Declaration of the International humanist and Ethical Union. Some others include:
…a commitment to the perspective, interests and centrality of human persons; a belief in reason and autonomy as foundational aspects of human existence; a belief that reason, scepticism and the scientific method are the only appropriate instruments for discovering truth and structuring the human community; a belief that the foundations for ethics and society are to be found in autonomy and moral equality…
– Concise Routledge Encyclopedia of Philosophy
An appeal to reason in contrast to revelation or religious authority as a means of finding out about the natural world and destiny of man, and also giving a grounding for morality…Humanist ethics is also distinguished by placing the end of moral action in the welfare of humanity rather than in fulfilling the will of God.
– Oxford Companion to Philosophy
Believing that it is possible to live confidently without metaphysical or religious certainty and that all opinions are open to revision and correction, [Humanists] see human flourishing as dependent on open communication, discussion, criticism and unforced consensus.
– Cambridge Dictionary of Philosophy
That man should show respect to man, irrespective of class, race or creed is fundamental to the humanist attitude to life. Among the fundamental moral principles, he would count those of freedom, justice, tolerance and happiness…the attitude that people can live an honest, meaningful life without following a formal religious creed.
– Pears Cyclopaedia, 87th edition, 1978
Rejection of religion in favour of the advancement of humanity by its own efforts.
– Collins Concise Dictionary
A non-religious philosophy, based on liberal human values.
– Little Oxford Dictionary