In this quote Seth points out that “we are what we think” … not the usual adage “we are what we eat”.
Some sources refer to the body literally as a “thought form” … but those are generally considered different from the physical body that we use to consciously perceive the moment of reality that we present to ourselves. Thought forms and personality fragments are like tracks we leave behind us … but since everything is consciousness, these tracks themselves are conscious and evolve in pursuit of the fulfillment of All That Is.
Not only is the body that we perceive arising from our inner world of thought in each moment that we manifest - but the entire perceived world around us arises seamlessly along with it as one event. It’s like being in a video game where you (actually your avatar) and the entire surrounding context (the perceived “external” environment) arise at once, 55 times a second.
I think Dogen, and other Buddhist masters, understood that when they made statements like “you define yourself too narrowly”. The “you” they spoke of was your entire subjective awareness (there is no objective “other” reality).
“Your physical body is, as an entity, the fleshed-out version – the physically alive version – of the body of your thoughts. It is not that your thoughts just trigger chemical reactions in the body, but that your thoughts have a chemical reality besides their recognizable mental aspects. I will have to use an analogy. It is not the best, but I hope it will get the point across: It is as if your thoughts turned into the various appendages of your body. They have an invisible existence within your body as surely as viruses do. Your body is composed not only of the stuff within it that, say, X-rays or autopsies can reveal, but it also involves profound relationships, alliances and affiliations that nowhere physically show. Your thoughts are as physically pertinent to your body as viruses are, as alive and self-propagating, and they themselves form inner affiliations. Their vitality automatically triggers all of the body’s inner responses. When you think thoughts, they are conscious. You think in sentences, or paragraphs, or perhaps in images. Those thoughts, as clearly as I can explain this, rise from inner components of which you are unaware.”
(The Individual and the Nature of Mass Events, Session 841)