He lived at Middletown with his grandmother during childhood, and prior to his entering college he had read widely in English literature and history, had excelled in Greek and Latin work, and had studied several modern languages.

He gave many hundreds of lectures, chiefly upon American history, in the principal cities of the United States and Great Britain.

In a letter from Charles Darwin to John Fiske, dated from 1874, the naturalist remarks: "I never in my life read so lucid an expositor (and therefore thinker) as you are."

Nineteenth-century enthusiasm for brain size as a simple measure of human performance, championed by scientists including Darwin's cousin Francis Galton and the French neurologist Paul Broca, led Fiske to believe in the racial superiority of the "Anglo-Saxon race".

Indeed, so anti-slavery was he that twenty-three years after the cessation of the American Civil War, he declared the North's victory complete "despite the feeble wails" of "unteachable bigots.

In books such as Outlines of Cosmic Philosophy (ISBN 0-384-15780-7), Fiske aimed to show that "in reality there has never been any conflict between religion and science, nor is any reconciliation called for where harmony has always existed."

[3] Of these, in The Destiny of Man Viewed in the Light of his Origin (1884), he argues that intellectual force is a later, higher and more potent thing than bodily strength, leading to a moral and non-selfish line of thought.