People often talk about Plotinus' system. The reason they do this is that Plotinus postulated a kind of series or chain of principles, so at the top there's what he called the One. Below the One is what he called Intellect. Below Intellect is Soul, and the effect of the soul is the physical world that we actually live in.
I was trained in Army Intelligence, but spent most of my army career in the infantry. But like many people of my generation, I was very much caught up in the Cold War, and books and movies about espionage.