When I first saw "tripartite" I thought it might be some ancient Greek word for a single country where three separate cultures practice racial segregation against each other, but I was wrong again; it was just Plato working overtime.
According to the ancient Greek philosopher, the soul consists of a "tripartite" of reason, spirit, and appetite. Personally, I found Plato's order of the tripartite to be in error. I would place "appetite" above "spirit" for what I feel is a fairly obvious reason.
To read more of this post, and my humble thoughts, on Plato's tripartite theory of the soul, please follow the attached link: Plato's Theory of Soul