Who can understand the Bible in any real depth? According to Paul, who was writing under inspiration, only a Christian can. Look at what he wrote in his letter to the church at Corinth:

1 Corinthians 2:10-15 (NASB)

“For to us God revealed them through the Spirit; for the Spirit searches all things, even the depths of God. For who among men knows the thoughts of a man except the spirit of the man which is in him? Even so the thoughts of God no one knows except the Spirit of God.

Now we have received, not the spirit of the world, but the Spirit who is from God, so that we may know the things freely given to us by God, which things we also speak, not in words taught by human wisdom, but in those taught by the Spirit, combining spiritual thoughts with spiritual words.

But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised. But he who is spiritual appraises all things, yet he himself is appraised by no one.”

First off, just to be clear, when Paul says “we” here, he means himself and those he is addressing, not just the apostles. Later in the passage he contrasts the “we” with “natural men”, not with everyday Christians.

The natural man here is the lost sinner, left to rely on his physical senses alone. To a lost person, the Bible often makes no sense. Paul doesn’t say it is hard or difficult for someone to understand the Bible without the Spirit. He says it is impossible! They cannot! But the spiritual man, who according to the Greek means a regenerate man who has the indwelling Holy Spirit promised in Acts 2:38 and elsewhere does have the ability to understand the Bible, which was inspired/spoken by the Spirit of God. He doesn’t need some supernatural event to happen anew each time he reads the Bible. The Spirit has been in him or her since salvation.

Romans 8: 7 says,”For the mind that is set on the flesh is hostile to God, for it does not submit to God’s law; indeed, it cannot. Those who are in the flesh cannot please God.” Not might not, or usually won’t, but it cannot!

And earlier in this letter Paul has written that “the word of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.” (1 Corinthians 1:18). The reason a lost person cannot understand the Bible is because they have been blinded by the Devil.

2 Corinthians 4:3-4

And even if our gospel is veiled, it is veiled to those who are perishing, in whose case the god of this world has blinded the minds of the unbelieving so that they might not see the light of the gospel of the glory of Christ, who is the image of God.

So do we need the Holy Spirit in order to understand the Bible? The New Testament says an emphatic “yes”. Without the Spirit we cannot understand the deep things of God, our minds are hostile to God, and we are blind. Only the Spirit can set humans free and allow the to see the message God is communicating in the Word, and that Spirit continually indwells believers. So if we have been born again, our lack of biblical understanding is our own fault.