[Peter] not only calls the unbelieving foolish, but also points out the reason why they slandered, even because they were ignorant of God. But inasmuch as he makes the unbelieving to be without understanding and reason, we hence conclude, that a right understanding cannot exist without the knowledge of God. How much soever, then, the unbelieving may boast of their own acuteness, and may seem to themselves to be wise and prudent, yet the Spirit of God charges them with folly, in order that we may know that, apart from God, we cannot be really wise, as without him there is nothing perfect.*
*J. Calvin, Commentaries on the Catholic Epistles (p. 83).