At a theoretical level, I think a naturalist approach to religion is just asking questions I'm not interested in. They're perfectly legitimate in their own terms, but they don't address the actual experience of how one or other aspect of religion becomes existentially meaningful to us in our actual lives. The fact that we ourselves are the subject of investigation makes all the difference.

In a sense these are questions that most people ask themselves to some extent. They become philosophical when asked with a persistence and rigour that pushes past conventional or evasive answers. It's nothing to do with acquiring a technical facility in an academic discipline.

Schleiermacher, however, starts by attempting to find what he takes to be a basic element of the human condition as such, namely, that we did not invent ourselves but find ourselves born into a life and a world that precedes us in manifold ways.

And perhaps this has to do with what I sense is a turning away from the idea of religion as being about conserving a certain heritage from the past towards religion as having to do with how we orientate ourselves to the future, to all we truly long for, to hope.

I'm not sure how far Derrida's later 'theological' interests are really rooted in post-structuralism or whether they don't rather reflect a kind of Kantian-Marxist trajectory - with a French twist on the centrality of liberty, equality and fraternity (cf. Politics of Friendship). Not to mention the role of Levinas and, behind Levinas, Judaism's twinning of eschatology and the call for justice.

Every stroke a tennis player plays is different, yet we perceive them as playing in a distinctive and unique way. It's what Heidegger called a certain 'how' of existing. It's ultimately always singular, and the double task of (a) getting it in view and (b) communicating it to others will inevitably be marked more often by failure than success!

It seems that just Being, the sheer fact of existence, that there is something rather than nothing, already inspires a wonder akin to religion. But - as in my comment about the Kingdom of God in the last answer - Jewish and Christian traditions are also prepared to challenge what 'is' for the sake of what could be.