I know a very similar question was asked only recently by @Bradley Wilson, and another similar question was asked by @Beofett over a week ago, but the specific situation and also the cultural context are very different here, so please don't close my question as a duplicate!
Note 2: The specific religion in question is not relevant because this situation occurs similarly in every religion here. I have added the India tag as a matter of course but feel this type of religious issue would be universal, so I welcome answers from members all over the world.
Now India has always been a very spiritual country and (not all but most) people of all faiths tend to be quite religious here. They also assume that others are similarly spiritual, even if they are members of other religions.
My distant relative who lives in the same city is such a person. He is 66 and a highly qualified Retired Professor of Commerce who happens to have become more religiously conscious over the years and 'feels the divine grace' all around him. That is very fine indeed but for the fact he assumes I feel similarly.
This is, of course, a typical assumption here, but it is a fact that I don't feel the divine grace all around me. I was given quite a religious upbringing but was always lukewarm towards religion and since I never felt the divine grace they talk about, I have never really been much of a believer, formally rejecting religion in private when I reached my mid-twenties. I am not against religious belief and might even believe in a 'higher power' myself if I later experience the divine grace conclusively, but I am not at all the type of firm believer he imagines me to be, at present.
Uncle has been visiting me once in a while and discusses 'spiritual matters.' He is luckily not much for religious rituals and suchlike, but talks to me with the implicit presumption that I too am spiritually inclined and feel the divine grace. He even sometimes asks me about my religious experiences. This puts me in a false position because I am trapped in having to choose between insincere agreement with him and explicit rejection of his ideas. I have uneasily agreed with him so far without much conviction.
The problem is that I can't tell him straight out that I don't really believe in his religion (into which I was born and of which I am a nominal member) or indeed in any other religion or divinity because he would be shocked and possibly tell other relatives and even mutual friends, which is inconvenient for me and culturally awkward in a predominantly religious society. I also don't want to discuss my lack of belief with Uncle or anybody else who might possibly make it their mission to bring me 'back onto the spiritual path.'
Please note that it wouldn't be a real liability for me to tell Uncle or anyone else that I am not their type of believer, and there are no serious social consequences to that nowadays in India, at least in my community, but I simply dislike the type of debate that will follow, demands for my reasons and possible efforts to make me a believer. So my real problem here is I don't want to be pushed into telling anybody that I lack religious belief. [Thanks to @deg who asked for this clarification.] That is why the 'direct' approach is not a genuine option. On the other hand, I feel uncomfortable with putting on a pretence of religiosity for the uncle's benefit, which also seems dishonest to my way of thinking.
So how to deal diplomatically with this person? My first tendency is to avoid him but that is hardly 'interpersonally intelligent', now is it! Please advise how to deal interactively and constructively with this situation.