A very large part of the problem between the views is really seen in the “extremes” of each.
(here comes the gross over simplications

)
The Catholic strenuously objects to the rather extreme views that we sometimes see in the faith alone, OSAS type communities…That all sin is forgiven and it doesn’t matter what they do, they can’t lose their salvation…A presumptuous view from the Catholic perspective.
The Non-Catholic objects to the equally extreme view that they see in many Catholics - sort of a sackcloth and ashes fear of embracing and assurance of salvation as our own…A sort of hopelessness in their eyes.
Of course, as is often the case, the truth lies in the middle.
As Catholics we DO need to embrace salvation as our own. Our belief, our Faith and our commitment to Christ gives us great assurance because of the Promises of our Lord and savior. This must be tempered though with the realization that we, imperfect creatures that we are, might still fall away…
And this is the thing that our non-catholic Brothers need to embrace…Assurance is not “Guarantee”…
Someone mentioned earlier the verse in 1 John 5:13
I write this to you who believe in the name of the Son of God, that you may know that you have eternal life.
This is often presented as evidence of “faith only” assurance. But what is not mentioned when this verse is proposed is what the “
this” is that John has written to them…Not just that verse, but the entirety of the Letter…All of the "If’s…Chapter 5, which contains the above verse starts off saying…
1 Every one who believes that Jesus is the Christ is a child of God, and every one who loves the parent loves the child. 2 By this we know that we love the children of God, when we love God and obey his commandments. 3
For this is the love of God, that we keep his commandments. And his commandments are not burdensome.
So We have eternal life - not just by our belief (faith) alone but by "Keeping God’s commandments…Shortly after the cited verse is this one - again, this is in the same chapter…
18 We know that any one born of God does not sin, but He who was born of God keeps him, and the evil one does not touch him.
So the question can then be asked…If one sins can one claim to be “born of God”?
Many more examples can be seen in this letter that call for action and right attitude. In chapter 4 we find this…
If any one says, “I love God,” and hates his brother, he is a liar; for he who does not love his brother whom he has seen, cannot love God whom he has not seen.
So … When John writes “I write this so that you know you have eternal life”…he is not writing simply of belief, but of belief that has action, conviction, and even struggle attached…If you Love God, you do not sin…If you hate your brother you do not Love God…If you love God you obey his commandments.
The Catholic may go a bit overboard on the side of caution, knowing how imperfect and sinful we are, but personally I’d rather not test our Lord by being too cocky and presumptuous…
I will go before Christ saying, "I am an unworthy servant, I have done only that which is required Luke17:10), in the hope that His response will be, "Well done Good and faithful servant…Now enter into the joy of your master (Mt25:21)
Peace
James