  Spinoza is claiming here that a mode X under the attribute of Thought is one and the same as mode X under Attributey. A good way to get some intuitive sense of this is to see how this works with respect to ourselves. Under the attribute of Thought, I am a finite mode—an idea or mind. Under the attribute of Extension, I am a finite mode, that is, a body. The claim in 2P7 and its scholium is that my mind (a mode of Thought) and my body (a mode of Extension) are one and the same. This is the case for all modes. Furthermore, whatever causal relation my body, say, bears to other modes of Extension, my mind will bear to the other modes of Thought. The understanding of this doctrine and its implications in more depth depends, probably more than any other doctrine, on how one construes other central elements of Spinoza’s theory of attributes (e.g. the number of attributes).  In Section 1.9.2 different directions of interpretation are considered regarding 2P7 and its scholium.