(lifted entirely from the monergism blog...)
A person may have well balanced theology, and his general views of truth would be considered evangelical and orthodox. And yet, thus far may he proceed in the deepest 'self deception'.
With all this "form of knowledge," this lodgment of the truth in the understanding, this subscription of the intellect to the doctrines of revelation, he is an utter stranger to that 'heart transformation', that inward illumination of the Holy Spirit, without which the soul is spiritually dead, the heart is unrenewed and unholy, and the whole man is unfit for the kingdom of heaven.
In short, we have here the case of one who, while his judgment assents to the truth, his heart entirely rejects it. The Gospel is to him a thing of intellectual subscription, and not of heart experience. Not a single truth of the Bible has become an element of life and holiness in his soul.
(From Octavius Winslow's, "The Coming of the Lord in its Relation to Nominal Christianity")