Newmans distinction is well known between notional and real assent. I have always felt that it had its roots in his evangelical conversion; certainly it was a frequent theme in his Anglican sermons. Here is an early example, from his sermon "Secret Faults," a reflection on the Psalm-verse: "Who has understood his errors? Cleanse thou me from secret faults" (Ps 19:12). It begins with the claim that "self-knowledge is a necessary condition for understanding" the great Christian truths:
Thus it is not too much to say that all those who neglect the duty of habitual self-examination are using words without meaning. The doctrines of the forgiveness of sins, and of a new birth from sin, cannot be understood without some right knowledge of the nature of sin, that is, of our own heart. We may, indeed, assent to a form of words which declares those doctrines; but if such a mere assent, however sincere, is the same as a real holding of them, and belief in them, then it is equally possible to believe in a proposition the terms of which belong to some foreign language, which is obviously absurd. Yet nothing is more common than for men to think that because they are familiar with words, they understand the ideas they stand for. Educated persons despise this fault in illiterate men who use hard words as if they comprehended them. Yet they themselves, as well as others, fall into the same error in a more subtle form, when they think they understand terms used in morals and religion, because such are common words, and have been used by them all their lives.Now (I repeat) unless we have some just idea of our hearts and of sin, we can have no right idea of a Moral Governor, a Saviour or a Sanctifier, that is, in professing to believe in Them, we shall be using words without attaching distinct meaning to them. Thus self-knowledge is at the root of all real religious knowledge; and it is in vain,worse than vain,it is a deceit and a mischief, to think to understand the Christian doctrines as a matter of course, merely by being taught by books, or by attending sermons, or by any outward means, however excellent, taken by themselves. For it is in proportion as we search our hearts and understand our own nature, that we understand what is meant by an Infinite Governor and Judge; in proportion as we comprehend the nature of disobedience and our actual sinfulness, that we feel what is the blessing of the removal of sin, redemption, pardon, sanctification, which otherwise are mere words. God speaks to us primarily in our hearts. Self-knowledge is the key to the precepts and doctrines of Scripture. The very utmost any outward notices of religion can do, is to startle us and make us turn inward and search our hearts; and then, when we have experienced what it is to read ourselves, we shall profit by the doctrines of the Church and the Bible.
He returns to the theme at the end of the sermon:
Can we content ourselves with such an unreal faith in Christ, as in no sufficient measure includes self-abasement, or thankfulness, or the desire or effort to be holy? for how can we feel our need of His help, or our dependence on Him, or our debt to Him, or the nature of His gift to us, unless we know ourselves? How can we in any sense be said to have that "mind of Christ," to which the Apostle exhorts us, if we cannot follow Him to the height above, or the depth beneath; if we do not in some measure discern the cause and meaning of His sorrows, but regard the world, and man, and the system of Providence, in a light different from that which His words and acts supply? If you receive revealed truth merely through the eyes and ears, you believe words, not things; you deceive yourselves. You may conceive yourselves sound in faith, but you know nothing in any true way. Obedience to God's commandments, which implies knowledge of sin and of holiness, and the desire and endeavour to please Him, this is the only practical interpreter of Scripture doctrine. Without self-knowledge you have no root in yourselves personally; you may endure for a time, but under affliction or persecution your faith will not last. This is why many in this age (and in every age) become infidels, heretics, schismatics, disloyal despisers of the Church. They cast off the form of truth, because it never has been to them more than a form. They endure not, because they never have tasted that the Lord is gracious; and they never have had experience of His power and love, because they have never known their own weakness and need.