Two years ago, I emailed some research to a Catholic theologian and friend who had challenged us in his Bible study on whether Catholics could be assured of salvation. Here's what I told him:

Assurance of salvation in the WLC:

Question 80: Can true believers be infallibly assured that they are in the estate of grace, and that they shall persevere therein unto salvation?

Answer: Such as truly believe in Christ, and endeavor to walk in all good conscience before him, may, without extraordinary revelation, by faith grounded upon the truth of God's promises, and by the Spirit enabling them to discern in themselves those graces to which the promises of life are made, and bearing witness with their spirits that they are the children of God, be infallibly assured that they are in the estate of grace, and shall persevere therein unto salvation.

Question 81: Are all true believers at all times assured of their present being in the estate of grace, and that they shall be saved?

Answer: Assurance of grace and salvation not being of the essence of faith, true believers may wait long before they obtain it; and, after the enjoyment thereof, may have it weakened and intermitted, through manifold distempers, sins, temptations, and desertions; yet are they never left without such a presence and support of the Spirit of God as keeps them from sinking into utter despair.

In our (i.e., Catholic) catechism, I find something else, in # 2005:

Since it belongs to the supernatural order, grace escapes our experience and cannot be known except by faith. We cannot therefore rely on our feelings or our works to conclude that we are justified and saved. However, according to the Lord's words—"Thus you will know them by their fruits"—reflection on God's blessings in our life and in the lives of the saints offers us a guarantee that grace is at work in us and spurs us on to an ever greater faith and an attitude of trustful poverty.

A pleasing illustration of this attitude is found in the reply of St. Joan of Arc to a question posed as a trap by her ecclesiastical judges: "Asked if she knew that she was in God's grace, she replied: ‘If I am not, may it please God to put me in it; if I am, may it please God to keep me there.'"

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Our prayers at Mass tell the story, I think. All this week I heard the following Prayer after Communion:

“Lord, look on your people with kindness and by these Easter mysteries bring us to the glory of the resurrection.”

It is ironic that prayers throughout the Mass have this begging quality, even during the Easter season when confidence in our resurrection ought to run high.

Just an interesting expression in the Catechism, “justification through faith and ... sanctification through charity” [# 2001]. Perhaps this joins Paul with James.

And in the same place, “God brings to completion in us what he has begun ...”. Sort of sounds a bit like assurance.