"...to discern both good and evil", doesn't that require a judgement?

Here is another in a long line of verses where we are told to make a judgement. 

Hebrews 5:12-14(NKJV)

For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. 

For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. 

But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil.

I especially like the way this is expressed.  God tells us to use our reason, our thinking minds.  We are told to discern good from evil.  How are we supposed to do that?  By studying God's word in my opinion.  You'll get all the guidance you could possibly need to discern good from evil in God's word!