but how do you with certainty determine whether they are
There is no certainty when it comes to another person, at least not right away. There is some patience required, it's a series of tests. For me at least, life isn't like the Mentalist TV show where you can instantly judge a person's character in 20 minutes. On the other hand, if they have a pattern of evil behavior going back 20 years, maybe rethinking being friends with them is a good idea.
To claim certainty is pride - I would rather live with the doubt and reversing mistaken decisions than turn into a vindictive monster. I believe that I have the best assessment of my character because I live in here, and thus I assume that everyone else knows themselves better than I know them. But I can get to 80%, and that's good enough. When one makes a character assessment, they walk the road between pride on one side and fear on the other. The fear of being wrong can paralyze. But most humans give enough information to act and test, which leads to more information, which leads to more action, which leads to more information, and so on.
The other problem is, this is literally a skill I had to learn by doing, to train myself to see patterns. Reading psychology books by Christian psychiatrists helped too. It took me 10 years of refining with mistakes to see the patterns of how people behave, and most people are too terrified of making one bad judgement to even begin. And even then, doubts still haunt me as to whether my judgement of character was correct.
But I had no choice. When I started learning this, I had a mental illness that constantly fed me negative information about other people and refused to see any positive qualities or hope in them at all. I had to fix that. However, an advantage of the starting position was that I didn't put my head in the sand as to people's negative qualities. I had to learn to be patient with the negatives I saw and see the assets each relationship brought into my life. But the odd part is that I had to fight the mental illness to build the assessment system I built in the previous post, so I'm not sure how the process would work for an ordinary person. I presume it would be a lot faster for a normal mind to learn.
Doesn't Jesus taught his disciples to be patient (up to 70 times x 7 times, which i believe means always) ?
Matthew 18:21-22 said:
21 Then Peter came up and said to Him, “Lord, how many times shall my brother sin against me and I still forgive him? Up to seven times?” 22 Jesus said to him, “I do not say to you, up to seven times, but up to seventy-seven times.
Okay, so the context of these verse is Matthew 18:15-20, where Our Lord outlined His church discipline process. Step 1: Go back to the Christian who has sinned against you in private. If they repent, forgive them and move on. Step 2: If they refuse to believe, bring a witness to their sin committed against you. If they repent, forgive them and move on. Step 3: If they refuse to repent, take it to the church for review. If they refuse to listen to the church's condemnation of their sin, excommunicate them, declare them an unbeliever, and kick them out.
The 490 forgiveness in Matthew 18:21-22 is contingent upon the repentance outlined in 18:15-20. This interprets the Scripture so it is consistent with itself. We are not called upon to forgive without confronting when a confrontation is warranted and thus become doormats for evil people. Please note also that forgiveness of 490 applies to believers in Christ who sin against you - verse 21 says "brother", which is the same "brother" in "if your brother sins against you" in verse 15 of the same passage. We have no such obligation toward the unbeliever, and the context of this passage is clearly about believers in Christ. And if we use the Bible as our standard of morality, we should presume that our brothers and sisters in Christ are not evil, at least not beyond correction. New believers would be confused, and fake believers would be evil and should be removed using the Matthew 18:15-20 system of confrontation that Christ outlined for us. A confused person would repent and turn from their sin, a mentally ill person would struggle and try to quit their sin and thus repent, but a fake believer would refuse to repent and thus be thrown out.
The turning the other cheek and going the extra mile verses are in the context of Christian submission to wicked governments who impose on people - do not resist government imposition of labor or inconvenience - rather than doing that for everyone. The Roman authorities of Jesus' day would force Jewish citizens to carry their packs, hence if they asked for one mile, give two. This would endear the Christian to the government rather than appearing like potential rebels. It's not about assessing character of people.