Christianity vs. Pluralism

I have made the decision to write my friend a letter. I could dialogue, but I would get better arguments in if I wrote a letter. My friend confesses Catholicism, but in reality is a Pluralistic whom thinks there are many ways to God. This is not what Roman Catholic soteriology teaches. How would you address Pluralism briefly in a short letter? My friend is not going to read a book, and I have dozens that address pluralism, but few can do it in a paragraph. Can you address pluralism in such a short space? I could build a case for the Bible, creationism, and such, but the pluralist won't deny the Bible is true, just will say its not the only way to Heaven so perhaps that approach won't work.

I am not Moral law only and this letter will prove that, however they should be a strong backbone to my letter.

What say you?