The Role of “spirit” in the Soul : Argument for the Tripartite Soul of Plato's Republic

According to Plato, the human soul is divided into three parts; “reason” , “sprit” and “desire” . What is the role of “spirit” ? There are three distinctive interpretations. 1. Actually, Plato meant that the soul is divided into two parts, “reason” and “desire”. 2. Actually, Plato meant that the soul is divided into four parts, “reason”, “upper spirit” , “lower spirit” and “desire”. 3. Plato divided the soul into three parts, as he wrote in Republic. I support the opinion 3. “Spirit” aids “reason” , and we can behave as “reason” commands