The "essence" of the principal contradiction,which was interpolated in Mao’s finalizing manuscript by Hu Qiao-mu,was proposed by Chen Bo-da at the Eighth Party Congress.It was approved by Mao through his pondering.The resolutions were adopted at the Eighth Party Congress and Mao didn’t bring up any counterviews.After the Eighth Party Congress,Mao criticized the "essence" of the principal contradiction,and then,negated the whole theory of the principal contradiction in the "Anti-Rightist Movement",replaced with the struggle between the two classes and the two roads.In May 1958,the Second Plenary of the Eighth Party Congress proposed the new principal contradiction that before socialist society was set up,the principal contradiction was the struggle between the proletariat and the bourgeoisie,the roads between socialism and capitalism.The negation of the principal contradiction proposed at the Eighth Party Congress is the historical point and the logic springboard of the mistakes in Mao’s later years.