Question 1 [of the Heidelberg Catechism] shows the glorious Reformation Protestant insight into the fact that assurance is to be the normal experience of every Christian believer and not simply the preserve of a few special saints who have been given extraordinary insight into their status before God, as was the medieval Catholic position.
This is perhaps one of the greatest Protestant insights of the Reformation. We live in an age where conversion to Roman Catholicism is not uncommon among those who have been brought up as evangelicals. There are many reasons for this: some speak of being attracted by the beauty of the liturgy in comparison with what is often seen as a casual and irreverent flippancy in evangelical services; others like the idea of historical continuity, of knowing where the church has been throughout history; still others find the authority structure to be attractive in an age of flux and uncertainty. Whatever the reasons, most Protestants would concede that Rome has certain attractions. Nevertheless, the one thing that every Protestant who converts to Rome loses is assurance of faith.
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The insight of the Reformation on assurance was key, theologically and pastorally. And, given that it is one thing that every convert to Roman Catholicism from Protestantism must lose, it is worth nothing its priority in the Heidelberg Catechism. The answer is so beautifully phrased; and yet if one ceases to be Protestant, one must cease to claim HC 1 as one’s own. That is a very high price to pay. Speaking for myself, all of the liturgical beauty of Rome, all of the tradition, all of the clarity and authority structure (and that clarity is often, I think, more in the eye of the beholder than the Church it itself) cannot compensate for the loss of the knowledge that I know I have been purchased by the precious blood of Christ that conversion to Rome requires."
Carl R. Trueman, The Creedal Imperative (Wheaton: Crossway, 2012),124-25.
HC 1, which Trueman alludes to, reads as follows:
Question 1. What is thy only comfort in life and death?
Answer: That I with body and soul, both in life and death, am not my own, but belong unto my faithful Saviour Jesus Christ; who, with his precious blood, has fully satisfied for all my sins, and delivered me from all the power of the devil; and so preserves me that without the will of my heavenly Father, not a hair can fall from my head; yea, that all things must be subservient to my salvation, and therefore, by his Holy Spirit, He also assures me of eternal life, and makes me sincerely willing and ready, henceforth, to live unto him.