Eric Steinhart here. I’ve been asked to clarify my terms, and it’s good to do so. As a philosopher, I always try to use terms in their most precise and specific senses.
The Theistic Deity. The theistic deity is a transcendental person who acts in the universe. The theistic deity is a being (it is not beyond being); it is maximally perfect; its main perfections are that it is all-powerful, all-good, and all-knowing; as such it is a rational moral agent, and therefore it is a person; the theistic deity is transcendent in the sense that it exists apart from any universe it creates; the theistic deity is active in the sense that causally interacts with things in the universes that it creates. (You can even find this as the specific sense of “theism” in the Wikipedia article.)
The Christian God is a specific type of theistic deity. It is distinct from both the Judaic and Islamic versions of the theistic deity (which are for instance non-triune).
There are lots of concepts of the divine in the West that are non-theistic. The Platonic Form of the Good is non-theistic; the Plotinian One is non-theistic; the deities of the Western mystical tradition are non-theistic; the deity of Spinoza is non-theistic; the deity of deism is non-theistic; the deities of pantheism and panentheism are non-theistic; the deity of Tillich is non-theistic. And (as I’ll argue) the deity of Wicca is non-theistic.
Atheism. I use “atheism” in its most precise and specific form: an atheist denies the existence of any theistic deity.
And I’ll note that these are very close to the definitions used in writers like Dawkins and Stenger. Stenger distinguishes between the theistic deity (he refers to it as “God”) and non-theistic deities (he refers to them as “gods”).
Other posts in the series so far: