If a lost person cannot discern truth from scripture, as some falsely teach
Lost people cannot discern the truth from Scripture, that is just a Biblical truth:
Romans 3:10-11 King James Version (KJV)
10 As it is written, There is none righteous, no, not one:
11 There is none that understandeth, there is none that seeketh after God.
1 Corinthians 2:14 King James Version (KJV)
14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
Understanding of Scripture, particularly the Mystery of the Gospel...has always been due to the Holy Ghost revealing truth to the natural heart. He did this throughout the entirety of the Old Testament, and it is His primary ministry as the Comforter:
John 16:7-9 King James Version (KJV)
7 Nevertheless I tell you the truth;
It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
8
And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:
9
Of sin, because they believe not on me;
He brings conviction to those who are of the world and not believing on Jesus Christ.
He also performs this ministry in our lives as Christians. Here is an example of Divine Revelation of Truth (and I am not saying the disciples were Christians, they were not, because they were not yet born again):
Matthew 16:13-17 King James Version (KJV)
13 When Jesus came into the coasts of Caesarea Philippi, he asked his disciples, saying, Whom do men say that I the Son of man am?
14 And they said, Some say that thou art John the Baptist: some, Elias; and others, Jeremias, or one of the prophets.
15 He saith unto them, But whom say ye that I am?
16
And Simon Peter answered and said, Thou art the Christ, the Son of the living God.
17
And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for
flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
The disciples did not "discern" truth, it was revealed to them. If anyone had a chance of "discerning" truth, it would have been the guys that ministered under Christ, who cast out demons, healed, and preached the Kingdom Gospel.
1 Corinthians 2:7-13 King James Version (KJV)
7
But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:
8
Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory.
9
But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.
10
But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
This passage, beginning in about v.16 of the previous chapter (and carrying on to the end of this one) is specific to the Mystery of the Gospel. The point being that the Mystery as well as those things we teach are taught to us by the Holy Ghost.
11
For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.
Likewise here.
And here...
12
Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.
13
Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.
All men, lost or saved, are dependant on God to reveal truth to them. This is the consistent pattern of Biblical History.
God bless.