Really interesting discussion. I like the distinction between "studying/being a scholar of theology" (possibly quite an erudite, advanced one), and doing Christian/Jewish/Islamic etc. theology.
As established in the thread, there are certainly aspects of the discipline of theology that one can do regardless of belief or lack thereof, e.g. New Testament studies/criticism. The textual sources, questions of what we can be fairly confident Jesus actually said or what was from the Evangelist, or the community they came from, etc. But if one then wants to ask "In the light of this, how do we understand the Gospels in relation to Christian faith, the nature and role of Jesus?" etc., then the non-Christian scholar must step back. (Except perhaps to say, my study of the New Testament leads me to the belief that there is no meaningful evidence of any supernatural aspect to Jesus's ministry, and thus I am not a Christian). Which does not make their scholarship any less valid or worthwhile, but it is a qualitatively different thing they are doing.
Conversely, a Christian scholar could be incredibly knowledgable about the Torah, its sources, social context, development, what different Rabbis have said about it, etc., so they could meaningfully do Torah scholarship in various ways, but if it comes to asking, "So how should we understand these commandments now, how is God speaking to us through this?", they can only answer that question as a Christian, so in that sense cannot be doing Jewish theology.
So I suppose it depends partly on what one means by ($Religion) theology!
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As established in the thread, there are certainly aspects of the discipline of theology that one can do regardless of belief or lack thereof, e.g. New Testament studies/criticism. The textual sources, questions of what we can be fairly confident Jesus actually said or what was from the Evangelist, or the community they came from, etc. But if one then wants to ask "In the light of this, how do we understand the Gospels in relation to Christian faith, the nature and role of Jesus?" etc., then the non-Christian scholar must step back. (Except perhaps to say, my study of the New Testament leads me to the belief that there is no meaningful evidence of any supernatural aspect to Jesus's ministry, and thus I am not a Christian). Which does not make their scholarship any less valid or worthwhile, but it is a qualitatively different thing they are doing.
Conversely, a Christian scholar could be incredibly knowledgable about the Torah, its sources, social context, development, what different Rabbis have said about it, etc., so they could meaningfully do Torah scholarship in various ways, but if it comes to asking, "So how should we understand these commandments now, how is God speaking to us through this?", they can only answer that question as a Christian, so in that sense cannot be doing Jewish theology.
So I suppose it depends partly on what one means by ($Religion) theology!