For professing themselves to be wise, they became fools.
John Gill
Professing themselves to be wise,.... The learned men among the Gentiles first called themselves "Sophi", wise men: and afterwards, to cover their wretched pride and vanity, "Philosophers", lovers of wisdom; but notwithstanding all their arrogance, their large pretensions to wisdom, and boast of it they became fools; they appeared to be so; they showed themselves to be such in those very things they prided themselves with the knowledge of: as, for instance, Socrates, after he had asserted the unity of God, and is said to die a martyr for the truth; yet one of the last actions of his life was sacrificing a cock to Aesculapius, at least he desired his friend Crito to do it.
Imported from an open dataset — not yet checked against the printed edition.