Soul, God, Spirit and invisible things in general are disputed by... Who? Who is doubting? Who is thinking? Speaking? You've probably heard words. Have you ever heard meaning? You've probably heard melody. Have you ever heard it begin or finish?
Look at the nearest window. Touch it. It is as real and measurable as anything; you can see and touch its edges. But... Really? Move in time or space, and everything's changed. What you see depends on where you look and vice versa, what you feel depends on how you touch - or push.
Everything visible, touchable etc. is and must be relative. The absolute things cannot be visible, you are not visible; what you see I cannot see the exactly same way; who you are I am not.