About Humanism
Like many belief systems, Humanism is specific to the individual; for every person you ask to define Humanism you will get a different answer. In general however, it is a belief system that puts at the center Humanity instead of any particular deity, but really it concentrates around thinking and reasoning as the basis for belief.
Early humanist thinking can be found in the Greek philosophers. Specifically Anaxagoras, who was described as the first free thinker, advocated science to understand the universe. A more common name might be Pericles who was a student of Anaxagoras and contributed to the development of freedom of thought and tried to expose superstitions for what they were.
But Humanism really came to light in the Renaissance with such notable thinkers as Thomas More and Erasmus. These were highly religious philosophers and thinkers that nevertheless espoused reason as the basis for belief and advocated the scientific method for discovery and proof of concepts. Humanism came to a head [with religion] with the trial of Galileo where people were forced to decide between rational thought and scientific enquiry and the dogmatic stance of the church with faith in the bible and the infallibility of the pope.
Modern Humanism is sometimes split into Secular Humanism and Religious Humanism. The later espouses some belief in a deity or supernatural being, but blends that with a stance that we have to evaluate our environment and life with reason and science. But Humanists in general don't differentiate between the two and believe that we have to use science and reason for our evaluation of everything. The difference lies in whether or not religion can stand up to such an evaluation.
So essentially modern Humanists are or quickly become moral and ethical atheists. To represent this view without the negative connotations of atheism, some have proposed the term Bright to mean "a person whose worldview is naturalistic, free of supernatural and mystical elements. A bright's ethics and actions are based on a naturalistic worldview." [Mynga Futrell] This is a community of people that rely on reason and thinking and not faith. Other terms that have been used for people or groups like this include Atheist, Humanist, Secular Humanist, Freethinker, Rationalist, Naturalist, Agnostic, and Skeptic.