What does "principle" mean here?

What's the meaning of principle in this definition of soul from Dictionary.com as in body and soul?

the principle of life, feeling, thought, and action in humans, regarded as a distinct entity separate from the body, and commonly held to be separable in existence from the body; the spiritual part of humans as distinct from the physical part.

Does principle in this context mean definition #7 of Google definition or does it mean something else that's not in this dictionary?

Actually, I could see #'s 6, 7 and 8 applying to the definition of "principle" as it relates to a component of a soul. It's more the context of the example that drives my answer, not just the definitions in abstract.