A soul is a very ambiguous word, but I believe that mind, consciousness, personality, personal identity (and soul whatever that might be) are all emerging phenomena that supervene on the physical brain.
What I consider the justification that supports my belief is the fact that all of it disappears when my brain is in a state of lower activity. That makes me believe that the brain activity produces all of it.
I do not consider the idea of soul just religious rhetoric. Plato was perhaps the father of dualism in philosophy, he distinguished between the realms of mind/soul (he forms) and the physical body. Descartes thoroughly examined the dualism of mind/soul stuff and body stuff. Neither did it in a context of religious rhetoric.
The concept of the human soul has been speculated by ancient philosophers and addressed in various mythological beliefs with a similar understanding of what exists in various religious philosophies. I think that most non-religious people have comprehended that life exists after death.
Modern religions inherited the idea from very ancient religious and mystical traditions who attributed agency and intentionality to almost everything. The ancient animists and the modern dualists alike have this sensation that we are not just body. It is indeed tempting to say that we can feel that we have a soul, but the idea that mind, consciousness, personality, personal identity are all emerging phenomena that supervene on the physical brain matches the same experience.
I examined the philosophical ideas in great detail and I am more a physicalist than a dualist or idealist. I believe in energy and there is clearly some kind of conscious observer driving the meat suit. Soul has a supernatural connotation. I don't believe anything exists beyond the laws of nature. Everything has an explanation, we just don't know it yet. I believe we are all part of the cosmic energy field, and therefore each other. We probably continue to exist, conservation of energy and all, but we don't go to heaven we just return to the source.