荀子的「性惡」論需要面對一個悖論：人類若無善因，「善」如何可偽呢？這個悖論涉及到荀子「性惡」論中「善」的起源問題。對於這個問題，學界提出了「心善」、「性善」、「偽善」（人為善）三種解釋方案，分別對應於荀子人性論的三種解讀：「性惡」論、「性善」論、「性樸」論。本文基於荀子人性論基本範疇和義理結構的分析，認為「性惡」、「性善」、「性樸」三種概括都與荀子人性論的義理結構不符，「心善」、「性善」、「偽善」三種解釋方案也都無法單獨解釋「善」的起源。「善」從積極的一面來說是源於先驗的德性，從消極的一面來說是源於才性的後天強化。欲性解釋了「善」為何必要，才性與德性解釋了「善」如何可能。

Xunzi’s theory of evil human nature has to face such a paradox: now that man has no inner good factor, how is human-effort good possible? This paradox relates with the problem of the origin of good in Xunzi. Scholars have offered three major solutions to this problem. The solutions are: 1. good heart-mind theory; 2. good human nature theory; 3. good human-effort theory. There are five major concepts included in these solutions: human nature, emotion, desire, heart-mind, talent. This paper concludes that Xunzi’s theory of human nature has a two-layer and three- dimension structure, based on the analysis of the above mentioned five major concepts. This paper argues that all the three solutions fail to explain the origin of good in Xunzi, except that we have a comprehensive hold of the structure of Xunzi’s theory of human nature.