Thank you for your call. I think we can get the simple answer to your question as we start with God as Mind. The offspring of Mind can only be thought. So the man (or manifestation) of Mind has to consist of thought. As Mind is the only source of thought, man is indeed the thinking that Mind is doing. This is why Principle (the one cause, source) cannot be in its idea. If you decide to cook something, the idea of what you want to cook is in your mind. But you are not in the idea. If you were, you would be subordinate to it. So man exists as the thinking, the expressing, the reflecting, the knowing, the experience of Mind itself. As we see that Mind is also Love, Truth, Life etc., it is clear that your whole existence is characterised by the thoughts that come from all these aspects of God.
“Principle and its idea is one…” (S&H 465:17); though not the same but two aspects of one being. Mind and manifestation exist as one consciousness. You cannot say where Mind stops and thinking starts. They are one. But Mind is not in its thinking. The thinking is in Mind. It’s like the singer and the song. You cannot say where the singer stops and the song begins.
Does this help? This is why you have dominion over body, because body is idea and your Mind is God.