「缺乏自制」在柏拉圖哲學中，出乎意外地不大具有份量。這並不吻合大多數人在道德實踐上遇到的困難。本文對此提出的理由是：如果「缺乏自制」意指一個人「明知道怎樣最好，卻沒這麼做」，那麼，柏拉圖《理想國》裡的「知識」可以完全避免這情形。但這嚴格意義的「知識」，必須透過漫長的教育，使心靈完全和諧一體。這裡試圖對柏拉圖既區分靈魂、又致力於心靈和諧一體的說法進行理解，將《理想國》第二、三卷的文藝教育整合在對心靈整體的教育藍圖中。以第四卷發展出來的靈魂三分說為理論背景，柏拉圖的文藝教育預設並促進心靈的合一，第十卷則反映出對心靈內在分歧的擔憂。文藝對於心靈合一與分歧的影響，正是心靈能否免於「缺乏自制」的關鍵。

But the Platonic knowledge must be attained via a long process of education which aims to accomplish the unity of the soul. This is not to ignore the partition of the soul in the Republic, but try to submit a more comprehensive interpretation which coherences Plato’s partition of the soul with his efforts on unifying it. The paper will read Plato's education in the arts within the context of his doctrine of the tripartite soul. Some scholars suggest that the education in the arts in books 2 and 3 is for the non-rational elements in the soul. I will challenge this view and provide a more holistic reading, along with Plato’s main argument for the tripartition in book 4. In my interpretation, the education in the arts plays a crucial role in integrating the soul in Plato’s whole educational scheme. This also explains why Plato criticizes poetry for its corrupting effects on the soul in book 10. A soul equipped with Plato’s knowledge will be free of akrasia. But, before the soul attains knowledge, the role of the arts in education is always Plato’s serious concern, for their power of unifying or partitioning the soul.