The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned. (1Co 2.14)
“Take notice that this is a moral ‘cannot,’ not a physical ‘cannot.’ When Paul says, ‘The natural person…is not able to understand them,’ he means that the heart is so resistant to receiving them that the mind justifies the rebellion of the heart by seeing them as foolish. This rebellion is so complete that the heart really cannot receive the things of the Spirit. This is real inability. But it is not a coerced inability. The unregenerate person cannot because he will not. His preferences for sin are so strong that he cannot choose good. It is a real and terrible bondage. But it is not an innocent bondage.”-- (John Piper, Finally Alive), p. 52
-- reformationtheology.com