I think he's only considered an intellectual and an expert in his field because other rhetoricians don't want to admit that they have no idea what he's saying. Here's a quote from Toulmin's The Uses of Argument.

"What things about the modes in which we assess arguments, the standards with reference to which we assess them and the manner in which we qualify our conclusions about them, are the same regardless of field (field-invariant), and which of them vary as we move from argument in one field to argument in another field (field-dependent)?"

Sir, I have no fucking clue.