The Tripartite of the Soul

Plato believes that there are three parts to the soul, Reason, Spirit, and Appetite. Although I must agree with him that these things are key ingredients to the soul, I cannot help but wonder if that is all there is. So, if these parts are necessary conditions to the soul, are they also sufficient? The authors suggest that "reason, will, non-bodily motivations or drives, emotions, and bodily appetites" (80) are also necessary. I would even go as far as to suggest that the authors themselves left out a crucial part of the human soul, intuition. Everyone has their intuition, their 'gut reaction' to something, our instincts are born with us and die with us and should not, under any circumstances, be ignored. Anyways, if "spirit" is the equivalent of "passion" and "emotion", and "appetite" includes all bodily functions, Then the new list of conditions for the human soul would read Reason, Spirit, Appetite, Will, and Intuition, as I put in. But still, this seems somehow inadequate. Human beings are incredibly complex creatures. How can the human soul be reduced to these five simple things? Are we missing any other parts to this equation? If these parts of the soul are indeed necessary conditions, are they sufficient enough to cover all of humanity? And how do we decide which conditions are sufficient, and which are only necessary? What if a person is somehow psychologically impaired, and this distorts their ability to "reason"? Is "reason" still a component of their soul? How do we know that these things even exist in our souls? What if they exist solely in our minds? Thoughts, anyone?