>Can I be a reasonable judge, in the old sense of the word "reasonable"? As in "And here we offer and present unto thee, O Lord, our selves, our souls and bodies, to be a reasonable, holy and living sacrifice unto thee."
When I first heard that sentence I thought it meant reasonable as in "appropriate" or "sensible" (i.e. not everything)! But my guess is that it does not mean that but it probably means something more like "intelligent" or "sound."
To be a reasonable judge of others means that I use my intellectual faculties to their fullest, both the analytical as well as intuitive and emotional sides, to grasp the full complexity that is a person – soul and body.
But to judge anyone I must begin with some prejudices (pre-judgments). These are critical. As a would-be judge must spend time working through my biases and predilections, not to necessarily purge out every vice (since that would be both impractical and impossible) but rather to know myself, to know where I am weak and where I need to be extra careful. I must spend time whittling down the log in my eyes so as to be able to help others with their specks.
I also must have some understanding of truth and reality. I must believe there is such as thing as perfect vision (20/20) and that it is objectively quantifiable (in a spiritual way).
You know how eye doctors use those eye charts with letters and numbers to test how accurate your vision is? And then they add some lenses and ask you to look again "Is it better now?" And so on. The process is very similar in spiritual life. We need to test our "normal" vision and find out how bad it is.
So the first test of "correct vision": can you see Jesus and Him only? If you can see Him clearly then your eyesight is fine. If not you need some corrective.
Second test is done in a community of believers where they are able to help you see better. Paul after the events on the road to Damascus needed that. Couldn’t Christ, after blinding him and making the point, have healed his blindness? Why would he need to get Ananias (Acts 9) to do the healing? I cannot say what God was thinking but it is very fortuitous that God chose another believer to be the one who brought sight to the new convert. The fellow believer;through prayer;is able to restore my sight, to bring me back into focus. their holy life and example, their faithfulness to the call, their willingness to come to me when I am still far from the church (though, of course already saved by God), and then to pray for me, is what brings out the healing of my sight.
The third test is ongoing. I am going for regular eye checkups. Every Sunday, in fact, I gather with fellow believers and we check each other's eyes. We greet each other in the Lord's name, we gather to worship Him, we share a meal, we study His Word. This helps me make sure I am still seeing clearly.
Now that the seeing part is clearer, now that I am actively engaged in whittling away the log in my eye, now that I have people praying for my vision I am now empowered to be able to judge reasonably another.