The following is from a work-in-progress called "Moby Dick: a Book Report" in which I read each chapter of Herman Melville's classic novel Moby Dick, and write about what I read.
As the Pequod sails on, it enters waters that are covered, for miles and miles, with a yellow substance called brit— small crustaceans that right whales feed upon. Ishmael is intrigued by the strange yellow blanket on the water: “we seemed to be sailing through boundless fields of ripe and golden wheat.” A pod of right whales appears the next day, and Ishmael marvels at the giants, eating brit and looking like mountains on the sea. The yellow brit and the swimming whales create the illusion of land.
And here Ishmael begins to ponder the philosophical differences between land (which is visible and known) and the sea (which is largely invisible and unknown). Humans still carry within them a primal sense of wonder and horror at the vast unknown of the ocean. Ishmael compares this land/sea dichotomy to human consciousness—our conscious mind is like a tiny island of “known” sitting upon a vast ocean of subconscious “unknown”. In this way, Melville is sort of predicting basic ideas of psychologist Sigmund Freud, who theorized that much of our behavior and identity is determined by our unconscious mind—which is only glimpsed in dreams.
Melville puts it this way: “Consider all this; and then turn to this green, gentle, and most docile earth; consider them both, the sea and the land; and do you not find a strange analogy to something in yourself? For as this appalling ocean surrounds the verdant land, so in the soul of man there lies one insular Tahiti, full of peace and joy, but encompassed by all the horrors of the half known life. God keep thee! Push not off from that aisle, thou canst never return!”