Not P but Moby-Dick (56)

[Mike Jing]

>From Chapter 80:

and remarking the depressions on one part of its summit, in phrenological
phrase you would say—This man had no self-esteem, and no veneration. And by
those negations, considered along with the affirmative fact of his
prodigious bulk and power, you can best form to yourself the truest, though
not the most exhilarating conception of what the most exalted potency is.

What is the author trying to imply here?