Complex sentence: He will not deny the implications, asserting that the great mystics have a point; only the modality of explication, of which Herrman's is predicated on reasoned principles of metaphysics.
Split into simpler sentences: He will not deny the implication, for he will assert that the great mystics have a point. All that differs is the modality of explication, of which Herrman's is predicated on reasoned principles of metaphysics.