Because Ra loves to describe parts threaded together into a whole as forming a “complex,” and because the mind/body/spirit became complex with the introduction of the veil (long story), and because…
Ra: “…mind, body, and spirit are inextricably intertwined and cannot continue, one without the other. Thus we refer to the mind/body/spirit complex rather than attempting to deal with them separately, for the work, shall we say, that you do during your experiences is done through the interaction of these three components, not through any one.” #30.2