Since physiognomy doesn’t teach us anything about the whale, Ishmael tries phrenology – a similar nineteenth-century pseudoscience in which you assess character according to the shape and bumps of the skull.
Unfortunately, the whale’s brain is tucked away in an odd part of its head, and the exterior appearance of the head isn’t related to the shape of the brain at all.
If you were to remove all the sperm oil from the whale’s head and then look at it from behind, it would look like a human skull, says Ishmael.
For a phrenologist, this skull would indicate an individual with "no self-esteem, and no veneration" (80.3) – in other words, no ego and no superego, no self-interest and no awe for others.
Next, Ishmael tries to develop his own form of phrenology based on the shape of the creature’s spine: the whale’s long, strong spine, he theorizes, might make up for its tiny brain.
The whale’s hump is caused by one of its larger vertebrae, and Ishmael makes this vertebrae represent the whale’s "indomitableness" (80.6).