1 Corinthians 3:18

Let no man deceive himself (Mhdei eauton exapatw). A warning that implied that some of them were guilty of doing it (mh and the present imperative). Excited partisans can easily excite themselves to a pious phrenzy, hypnotize themselves with their own supposed devotion to truth. Thinketh that he is wise (dokei sopo einai). Condition of first class and assumed to be true. Predicate nominative sopo with the infinitive to agree with subject of dokei (Robertson, Grammar, p. 1038). Paul claimed to be "wise" himself in verse Acts 10 and he desires that the claimant to wisdom may become wise (ina genhtai sopo, purpose clause with ina and subjunctive) by becoming a fool (mwro genesqw, second aorist middle imperative of ginomai) as this age looks at him. This false wisdom of the world ( Acts 1:18-20 Acts 1:23 ; Acts 2:14 ), this self-conceit, has led to strife and wrangling. Cut it out.

Read 1 Corinthians 3:18