本文從柏拉岡哲學與「哲人術」 (σοφιστκη /Sophistik) 的對抗作為研究的開始點，目的在研究柏拉圖用何種哲學方法從事這樣的哲學爭辯與思想對抗。本文首先研究亞里斯多德對於「哲人術」的界定， 從而將「哲人術」理解為：「哲人的意見是一種錯誤的言論，這種言論混淆了『是』與『不是』，將『是』與『不是』之間的關係做了錯 誤的分離或者結合；或者可以這麼說，哲人的意見是『不是』當作『是』，或者將『是』當作『不是』的一種『現有的是』，或者說，『不是』的『是』是一種『異的是』。」然後藉著 Diogenes Laertius 的記載， 來觀察辯證術與哲人術之間的爭執以及辯證術的特點。 Diogenes Laertius 講： 柏拉圖大抵使用「引入為證」）（σοφιστκη /induction）作為其證明的方式， 「引入為證」有二種：a、依據相反者（σοφιστκη /by the way of contradiction）， b、出自同意者（σοφιστκη /from the agreement）。分析了「依據相反者」和「出自同意者」的「引入為證」的論證效力之後，筆者發現這兩種推證的重要意義不在於：可靠且不可動搖的事實出發，用以建立知識，而只在於：在對話中，便對話者在論題上陷入兩難的困境。 然而這兩者的辯證方式不同，前者藉著前項與後項之間的內容有部分差異而否定其前後項之間的推論關係，藉以獲得互相相反的結論；後者 則不然，由前項與後項之間的內容同屬於某個更大的類，利用同屬於某類的性質，推斷前項與後項為同一，藉以突顯出其推論的荒謬性。

　　　　　This article begins from the standpoint that Plato's dialectical method is founded upon his antagonism of the Sophists. It aims at investigating how and in what way Plato succeeded in using the dialectical technique in expelling the Sophists from the realm of philosophy. Aristotle defines Sophism as “Sophism is a phenomenon and not concerned with wisdom. Sophists acquire money through the propagation of a wisdom which is not true.” Diogenes Laertius reports in his Vitae Philosophorum that Plato's dialectical ways of argumentation are inductive. This induction can then be divided into two types, way of contradiction and from the agreement. After analyzing Plato's two kinds of argumentation it can be said that their importance is not to be found in the acquiring of knowledge, but rather in exposing sophistic fallacies by way of paradoxical interpretation of their assertions. In Plato's dialogues the way of contradiction can be used to falsify an argument by differentiating between prior and posterior terms. The argument is then abolished. The method of the agreement must be abolished. The method of the agreement must be abolished because the prior and posterior terms mix with a greater genera which seems to identify both terms. Consequently, these two types of argumentation produce absurd results due to false reasoning.