Ecc 2:15 Then said I in my heart, As it happeneth to the fool, so it happeneth even to me; and why was I then more wise? Then I said in my heart, that this also is vanity. 

1 Corinthians 8:2 And if any man think that he knoweth anything, he knoweth nothing yet as he ought to know.

Heb 5:12-14 For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.  Heb 5:13 For every one that useth milk is unskilful in the word of righteousness: for he is a babe.  Heb 5:14 But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.