What is the difference between a soul and a spirit?

My roommate asked me to define the difference between a soul and a spirit? What do you say?

A soul, according to the original *Catholic Encyclopedia *is “the ultimate internal principle by which we think, feel, and will, and by which our bodies are animated.” In this case, the Catholic Encyclopedia is referring to human souls. A soul may be, for lack of a better term, “made up” of spirit or of matter. Human and angelic souls are spiritual souls; human souls differing in that they are embodied in matter while angelic souls are pure spirit. For human and angelic souls, the term spirit can either be a synonym for the term *soul *or it can refer to the soul’s composition. Animal and plant souls are material, which means that they cease to exist when the animal or plant dies. Since they are material souls, one would not use the term spirit in reference to animal or plant souls.

Recommended reading:
Soul
What Spirits Are and What They Aren’t by Frank Sheed

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