The ability to judge, to examine evidence, pro and con and come to a conclusion as to whether something (someone) is right or wrong. We do this every day, to one degree or another, about people, situations, problems that need solving and so on. The world is quick to pass judgment, especially on believers, and then they proceed to demand that we lay aside our ability and obligation to return the favor to them as they tell us we have no right to 'judge' them which is just another attempt to escape the knowledge and consequences of their own words and deeds.
For the believer there is one aspect of judging or discerning that the world does not hold itself to and that is to judge righteous judgment (John7:24). We are not allowed to pass by certain evidence that we do not like, or to pass over someone because they are 'well respected' in the 'church world.' If our judgment/discernment is to be seen as righteous then it must be without partiality. Our Lord is "no respecter of persons" (Acts 10:34 and Deut. 10:17) so how can we expect others to believe that we speak on God's behalf when we speak with favoritism on any level?
To be able to judge with righteous judgment one must know what is right (holy) and what is not (profane). This knowledge does not come by osmosis or an hour or so "at church" once a week. It comes by diligent study on a regular basis; by much prayer and searching of our heart, constantly; by laying down erroneous doctrines that we may hold dear, despite their unbiblical root. Isa. 28:9 & 10 and Heb. 5:13 & 14 tells us that there is a long, drawn out process, a life long and eternal process of learning about our God from our God. Determine which is better: to be cumbered about much serving or to sit at the feet of Jesus and learn from Him? Luke 10:38-42. Our 'senses' (spiritual senses) must be exercised or they will grow weak and useless. That is why we often face dilemmas and have unanswered questions about people and their teachings. We look every place but the right place for answers until we come to our senses and remember that the Word of God has the answer. Maybe, just maybe the Lord Jesus would like to walk with us and teach us from His Word. We, as His new creation, are His greatest pleasure. Yet do we deny Him His due by our stubbornness?
"Afresh, precious, precious Jesus, I resign this body to You, for doing or suffering, for living or dying. Will You accept it? Will You use me for Your glory more than heretofore, that You may have some little return for all the benefits You have done to me? Oh, do grant this request; my heart longs for it, my spirit pleads for it; and "if You will, You can." You know the hot temptation of which I am the subject. Bring Your glory out of it, and keep me from the evil, and it shall be well." - Ruth Bryan