1 Corinthians 2:14

But the natural man
Not a babe in Christ, one that is newly born again, for though such have but little knowledge of spiritual things, yet they have a taste, and do relish and desire, and receive the sincere milk of the word, and grow thereby; but an unregenerate man, that has no knowledge at all of such things; not an unregenerate man only, who is openly and notoriously profane, abandoned to sensual lusts and pleasures; though such a man being sensual, and not having the Spirit, must be a natural man; but rather the wise philosopher, the Scribe, the disputer of this world; the rationalist, the man of the highest attainments in nature, in whom reason is wrought up to its highest pitch; the man of the greatest natural parts and abilities, yet without the Spirit and grace of God, mentioned ( 1 Corinthians 1:20 ) and who all along, both in that chapter and in this, quite down to this passage, is had in view: indeed, every man in a state of nature, who is as he was born, whatever may be the inward furniture of his mind, or his outward conduct of life, is but a natural man, and such an one

receiveth not the things of the Spirit of God:
not the things relating to the deity, personality, and perfections of the Holy Spirit, though these the natural man knows not, nor receives; nor the things done by him, particularly the operations of his grace on the souls of men in regeneration, concerning which he says, as Nicodemus did, "how can these things be?" but the truths of the Gospel before spoken of; so called, because they are contained in the Scriptures edited by the Spirit of God, are the deep things of God, which he searches into and reveals; and because they are made known by him, who is given and received for that end and purpose, that the saints might know them; and because they are delivered by the preachers of the Gospel, in words which he teacheth; now these the natural man receives not in the love of them, so as to approve of and like them, truly to believe them, cordially embrace them, and heartily be subject to them, profess and obey them, but on the contrary abhors and rejects them:

for they are foolishness unto him;
they are looked upon by him as absurd, and contrary to reason; they do not agree with his taste, he disrelishes and rejects them as things insipid and distasteful; he regards them as the effects of a crazy brain, and the reveries of a distempered head, and are with him the subject of banter and ridicule:

neither can he know them:
as a natural man, and whilst he is such, nor by the help and mere light of nature only; his understanding, which is shut unto them, must be opened by a divine power, and a superior spiritual light must be thrown into it; at most he can only know the literal and grammatical sense of them, or only in the theory, notionally and speculatively, not experimentally, spiritually, and savingly:

because they are spiritually discerned;
in a spiritual manner, by a spiritual light, and under the influence, and by the assistance of the Spirit of God. There must be a natural visive discerning faculty, suited to the object; as there must be a natural visive faculty to see and discern natural things, so there must be a spiritual one, to see, discern, judge, and approve of spiritual things; and which only a spiritual, and not a natural man has.