Sadly there are not a lot of extra-biblical sources on Jesus and his life actually.
There is one, a single one. And it’s pretty bad. Josephus. He basically mentions “James, the brother of Jesus they call Christ”, in the middle of a text not about Jesus at all.
“Soul” is just consciousness. Which many people seem to equate to the brain here.
There is 0 scientific evidence that consciousness has anything to do with our brains. Much to the contrary actually.
Consciousness truly is one of the biggest mysteries of life. We all experience it, but the more you observe it, the less you can find it.
It may feel at first as it’s a phenomena of the brain, of the mind. But soon after you start paying really close attention to it, you realize that consciousness is behind the mind. It’s underneath it.
It observes the mind. It observes everything. And that’s what it is. Perceiving. Aware of everything.
Its the only indivisible and irreducible thing in the universe that we ever found. Consciousness just is. It is the awareness in you. It is the awareness in everything.
When we crack consciousness, all these talks of “souls”, “god”, “atheism”, will seem just silly tbh.