Most people, including many freethinkers, are unaware that notions such as atheism, agnosticism, skepticism and freethought all rely on a set of rules that are described by a particular system of philosophy. This philosophy, known as Naturalism, also describes the underlying logical framework for science itself.
The naturalistic worldview comprises the foundation for the beliefs of one whole faction of the fundamental divide between people on the nature of reality. There are those who don't believe in the supernatural, and those who do. The key point of difference between naturalists and non-naturalists is the subject of causation (interaction). Naturalists generally ascribe a causal reality to phenomena that are part of the natural world. This causal reality extends to ourselves, with sometimes startling and unintuitive consequences. However, many people who are atheists and freethinkers have not completely accepted the implications of naturalism on certain deeply ingrained culturally-reinforced beliefs such as free-will and consciousness.
But Naturalism goes beyond that. It offers a positive philosophy for atheists and freethinkers to coalesce under. It helps us rise above the denial of god and such things as spirits, ghosts and the supernatural. It gives us an affirmative belief system, one that can provide more meaning and purpose than any religion can.
Naturalism can offer a complete worldview if the principles of naturalism are applied to our lives, to critically examine concepts such as consciousness, ego, self, free-will, love, compassion and perhaps even the meaning of life.