The first stumbling block that I would like to remove is terminology. Some of this may seem quite elementary to some of you, but there have been an unbelievable number of arguments that could've been avoided altogether if it weren't for common misunderstandings of various terminology. As I told someone during a discussion some time ago, "Words do have meanings. To strip down the meaning of a word and assign it a new meaning that is better suited to prop up your argument is like playing tennis without the net."
Theism
Oxford defines theism: Belief in the existence of a god or gods, especially belief in one god as creator of the universe, intervening in it and sustaining a personal relation to his creatures.
From the Concise Encyclopedia:View that all observable phenomena are dependent on but distinct from one Supreme Being. The view usually entails the idea that God is beyond human comprehension, perfect and self-sustained, but also peculiarly involved in the world and its events. Theists seek support for their view in rational argument and appeals to experience. Arguments for God's existence are of four principal types: cosmological, ontological, teleological, or moral. A central issue for theism is reconciling God, usually understood as omnipotent and perfect, with the existence of evil.
In short, theism is the belief in a god or gods. Theists are subscribers to this belief. Hindus, Muslims, Christians, Wiccans, and Scientologists are all examples of theists. (I could also add in Jews, but I won't. While most Jewish people believe in a god, atheism is a viable position to hold as a Jew among the Jewish community.You cannot say this about the others. One cannot be an atheist Christian or an atheist Muslim, as examples.) It is derived from the Greek, theos, god+ism.
Deism
Oxford defines deism: Belief in the existence of a supreme being, specifically of a creator who does not intervene in the universe. The term is used chiefly of an intellectual movement of the 17th and 18th centuries that accepted the existence of a creator on the basis of reason but rejected belief in a supernatural deity who interacts with humankind.
Deism differs from theism in only one way, the idea that god does or does not intervene in the affairs of mankind. A theist and a deist could, technically, share a belief in the same god. Their only point of contention would be whether or not that shared god intervenes in any way in our day-to-day lives. Deism derives its root from the Latin, deus, meaning god+ism.
Pantheism
Oxford defines pantheism: A doctrine that identifies God with the universe, or regards the universe as a manifestation of God.
In this case, a pantheist is one who believes that the universe is god. Generally, pantheists are tolerant of many religious beliefs because, as the saying goes, all roads lead to Rome. The pantheist holds that whether you worship a specific god or a multitude of gods, the universe is inclusive of them all.
The next two terms are where things tend to get heated when two people are arguing. I am going to lay out their definitions first, and then I'm going to try to clear up any misconceptions that both theists and atheists alike have with them.
Agnostic
Oxford defines the term agnostic in this way: a person who believes that nothing is known or can be known of the existence or nature of God or of anything beyond material phenomena; a person who claims neither faith nor disbelief in God.
Atheism
This definition is short and to the point. Again, from Oxford: Disbelief or lack of belief in the existence of God or gods.
A Short Diatribe on the Terms So Far...
Most people don't have any problems with the first three terms, theism, deism, and pantheism. Most of the arguments and misconceptions come from the terms atheism and agnostic.
