ok, but how do i get from there to discerning genuine believers from fake by basically asking them how they feel?
the implied question of the video is, here's a random person who professes to be a Christian, what questions can you ask to discern whether they really are or not? i.e. how can a person separate wheat from chaff by holding a 5 to 10 minute conversation with someone who claims to be a believer?
i was surprised to hear questions about the person's emotional state, rather than questions about what they believe. i'm not sure i'm following Keller's logic.
We are saved by grace through faith in Jesus. The result of this faith is works. Without works there is no real faith. The works doesn't save but it is evidence of faith. No works no faith. So to discern if someone is saved look at their works. 2 sections of scripture on this.
James 2 NIV
Faith and Deeds
14 What good is it, my brothers and sisters, if someone claims to have faith but has no deeds? Can such faith save them? 15 Suppose a brother or a sister is without clothes and daily food. 16 If one of you says to them, “Go in peace; keep warm and well fed,” but does nothing about their physical needs, what good is it? 17 In the same way, faith by itself, if it is not accompanied by action, is dead. 18 But someone will say, “You have faith; I have deeds.”
Show me your faith without deeds, and I will show you my faith by my deeds.
19 You believe that there is one God. Good! Even the demons believe that—and shudder. 20 You foolish person, do you want evidence that faith without deeds is useless? 21 Was not our father Abraham considered righteous for what he did when he offered his son Isaac on the altar? 22 You see that his faith and his actions were working together, and his faith was made complete by what he did. 23 And the scripture was fulfilled that says, “Abraham believed God, and it was credited to him as righteousness,” and he was called God’s friend. 24 You see that a person is considered righteous by what they do and not by faith alone. 25 In the same way, was not even Rahab the prostitute considered righteous for what she did when she gave lodging to the spies and sent them off in a different direction? 26 As the body without the spirit is dead, so faith without deeds is dead.
In addition here is Matthew.
Matthew 7 AMPC
15 Beware of false prophets, who come to you dressed as sheep, but inside they are devouring wolves.
16 You will fully recognize them by their fruits. Do people pick grapes from thorns, or figs from thistles?
17 Even so, every healthy (sound) tree bears good fruit [worthy of admiration], but the sickly (decaying, worthless) tree bears bad (worthless) fruit.
18 A good (healthy) tree cannot bear bad (worthless) fruit, nor can a bad (diseased) tree bear excellent fruit [worthy of admiration].
19 Every tree that does not bear good fruit is cut down and cast into the fire.
20 Therefore, you will fully know them by their fruits.
21 Not everyone who says to Me, Lord, Lord, will enter the kingdom of heaven, but he who does the will of My Father Who is in heaven.
22 Many will say to Me on that day, Lord, Lord, have we not prophesied in Your name and driven out demons in Your name and done many mighty works in Your name?
23 And then I will say to them openly (publicly), I never knew you; depart from Me, you who act wickedly [disregarding My commands].