The existence of soul is a serious problem examined by philosophy. Like you or not.
I know you don't recognise any other philosophical method rather than the scientific one.
https://global.britannica.com/topic/soul-religion-and-philosophy
The philosophy branch that studies the soul is called Metaphysics.
And Philosophy of mind approach the concept of soul in the Mind-body problem. Neuroplasticity shows that the mind itself can control the material organisation of the brain.