I don't believe in anything, especially duality.
Very few people who do would dream of calling themselves atheists.
Well, I just read the passage in Descartes's "Discourse on the Method of Rightly Conducting the Reason, and Seeking the Truth in the Sciences" where the principal of "cogito ergo sum" appears. And although he appeared to be some kind of light theist, shortly after this he appears to make several dualism statements in riffing off that idea. And even if he was some kind of light theist, I think these ideas can probably be subtracted from theism.
He says: "In the next place,I attentively examined what I was and as I observed that I could suppose that I had no body, and that there was no world nor any place in which I might be; but that I could not therefore suppose that I was not; and that, on the contrary, from the very circumstance that I thought to doubt of the truth of other things, it most clearly and certainly followed that I was; while, on the other hand, if I had only ceased to think, although all the other objects which I had ever imagined had been in reality existent, I would have had no reason to believe that I existed; I thence concluded that I was a substance whose whole essence or nature consists only in thinking, and which, that it may exist, has need of no place, nor is dependent on any material thing; so that " I," that is to say, the mind by which I am what I am, is wholly distinct from the body, and is even more easily known than the latter, and is such, that although the latter were not, it would still continue to be all that it is."
So there you have it. Existing, thinking is something that has a feeling of being something that can be non-local to a physiological system.