Martin had ascended from pitch to pitch of intellectual living and here he was at a higher pitch than ever. All the hidden things were laying their secrets bare. He was drunken with comprehension. At night, asleep, he lived with the gods in colossal nightmares; and awake, in the day, he went around like a somnambulist, with absent stare, gazing upon the world he had just discovered." [Chapter 13]

As was the case with the fictional Martin Eden, London was highly influenced by Spencer. It was a fascination that lasted throughout his life. Spencer is especially important in understanding Jack London's racialism.

Contrary to popular belief, it was Herbert Spencer, not Charles Darwin, that first coined the phrase "survival of the fittest." He first used the phrase in the Principles of Biology (1864 - 1867). Spencer wrote,

The survival of the fittest which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection, or the preservation of favored races in the struggle for life.

Spencer adapted the theory of evolution into a social system in which those individuals, species, or races with the best acquired characteristics would survive. Spencer's writings were particularly responsible for the rise of Social Darwinism in the late 19th century.