“Yet the LORD hath not given you an heart to perceive, and eyes to see, and ears to hear, unto this day.” 
(Deuteronomy 29:4)

These Phrases, an Heart to perceive, Eyes to see, and Ears to hear, mean an Ability, in a spiritual manner, to discern, receive, and delight in spiritual Things, because of their Excellency and Glory. Such a Perception, Embracement of, and Pleasure in heavenly Things, are intended, as issue in the Glory of God, and the Salvation of the Soul. Where of natural Reason is incapable, how much soever it may be cultivated and improved. This Ability, is not a Capacity to understand the Import of the Language of Scripture, concerning the most mysterious Doctrines which it contains. Such as the Doctrine of the Trinity; of the Incarnation of Christ; the Union of the Divine and human Natures, in His Person; of Regeneration; and of other sublime Truths. Nor is it a Power to discern the Dependence, Connection and Harmony, of evangelical Doctrines. Men in common are the Subjects of an Ability for the former, and of a Capacity for the latter; otherwise they could not be required to believe the Verity of those Doctrines, which are supernaturally revealed. The Reason why Men do not believe the Truths of the Gospel, is not the want of an Ability to understand the Language of Scripture, or of a Capacity to discern the Dependence, Connection and Agreement of evangelical Principles: But the Cause thereof is, they disapprove of them, and account them to be the very Reverse of what they are in fact. They are the Wisdom of God; but in the Esteem of natural Men, they are Folly, and therefore, unfit to be believed and embraced. On the contrary, they think they are to be despised and rejected, as irrational and absurd. The natural Man receiveth not the Things of the Spirit of God, to him they are Foolishness, neither can he know them, because they are spiritually discerned. He is a spiritual Man, who judges, or discerns spiritual Things themselves, and consequently, he must be possessed of a spiritual Ability. And that Ability is, a holy supernatural Principle, whereof the whole Soul is the subject, and it is permanent and abiding therein. From that Principle, all holy, spiritual Acts spring.

John Brine (1760)