Visible souls....

[The Saucepan Man]

Originally Posted by Lalwendë

... he is the one character we truly get into the head of, often distressingly so.

I would say that there are a few, albeit a limited number, of characters who might be described as having "psychological depth" in the modern sense, even though we do not "get into their heads" as such (or not all of them anyway). But, consistent in many ways with the thoughts expressed on this thread, they are invariably those who are, to one degree other, morally ambiguous. In addition to Gollum, I have in mind Boromir, Eowyn and Denethor.