[Boromir88]

Fordim, I think this is the Letter you are looking for?

The Lord of the Rings is of course a fundamentally religious and Catholic work; unconsciously so at first, but consciously in the revision. That is why I have not put in, or have cut out, practically all references to anything like 'religion', to cults or practices, in the imaginary world. For the religious element is absorbed into the story and the symbolism. ~Letter 142

Lal remarks in another thread that there is a difference between the English use of 'fundamental' and the American use of the word.

The word fundamentally, or 'fundamentals' means the basics, or doing the simple things right. Sort of like in baseball, when someone says he is a 'fundamentally sound player,' he does the basic things right...(using both hands to catch the ball, keeping your weight on your back foot when you swing, as some examples). It's the simple things, the basics.

In the UK Lal says that it typically means 'lazily' or 'sloppily.'

Looking at this, I think it looks like 'fundamentally religious and Catholic work' means the basics of Christianity are in the story and they are 'absorbed in the symobolism.' There is nothing that comes out and hits you over the head like 'That's obviously Christianity,' kind of like Hookbill's point about the subtetly of the books. (Though, as a side note, I've seen it argued showing the English usage of the word).

I would love to know more about why this happened. Is it just a middle aged/older man coming closer to his doom and dwelling on questions of ultimate fate?~Child

It may have been something that happened as he got older, or at least he started thinking more about when he got older. Tolkien wrote repeatedly that he got sick quite a bit as his age increased, his health got worse, and he wrote about needing to 'rest.' Also as Simon remarks in some memories he had with his grandfather:

He was capable of extremely minute penwork and once gave me a farthing on which he'd written the entire Lord's Prayer in circular script.

I vividly remember going to church with him in Bournemouth. He was a devout Roman Catholic and it was soon after the Church had changed the liturgy from Latin to English. My grandfather obviously didn't agree with this and made all the responses very loudly in Latin while the rest of the congregation answered in English. I found the whole experience quite excruciating, but my grandfather was oblivious. He simply had to do what he believed to be right. He inherited his religion from his mother, who was ostracised by her family following her conversion and then died in poverty when my grandfather was just 12. I know that he played a big part in the decision to send me to Downside, a Roman Catholic school in Somerset.