In a very old but still relevant article titled, "A Theory of Moby Dick," author William S. Gleim argues that for Ahab, "the only escape from the torture of consciousness, as he felt it, was through either faith or insanity. He was the victim of his own cogitations concerning the unknowable; yet he could not resist the urge of inquiry as he confesses: "I love to sail forbidden seas and land on barbarous coasts." This is a typical line with a double meaning, for literally it describes his personal experience; but figuratively, it reveals his passion for speculating on the mysteries of the infinite."
"A Theory of Moby Dick"
William S. Gleim The New England Quarterly
, Vol. 2, No. 3. (Jul., 1929), pp. 402-419.