"A Hearing for Vavilov", p. 144
Hen's Teeth and Horse's Toes (1983)
“In fact, for a voluntarist like Schopenhauer, a theory so sanely and cautiously empirical and rational as that of Darwin, left out of account the inward force, the essential motive, of evolution. For what is, in effect, the hidden force, the ultimate agent, which impels organisms to perpetuate themselves and to fight for their persistence and propagation? Selection, adaptation, heredity, these are only external conditions. This inner, essential force has been called will on the supposition that there exists also in other beings that which we feel in ourselves as a feeling of will, the impulse to be everything, to be others as well as ourselves yet without ceasing to be what we are.”
The Tragic Sense of Life (1913), VII : Love, Suffering, Pity
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Miguel de Unamuno 199
19th-20th century Spanish writer and philosopher 1864–1936Related quotes
"Double Trouble", pp. 38–40
The Panda's Thumb (1980)

Quote of Kandinsky, in Paris, March 1935; as cited in Artists on Art – from the 14th – 20th centuries, ed. by Robert Goldwater and Marco Treves; Pantheon Books, 1972, London, p. 451
1930 - 1944

Don Soderquist “ The Wal-Mart Way: The Inside Story of the Success of the World's Largest Company https://books.google.com/books?id=mIxwVLXdyjQC&lpg=PR9&dq=Don%20Soderquist&pg=PR9#v=onepage&q=Don%20Soderquist&f=false, Thomas Nelson, April 2005, p. 81.
On working hard

Source: Selected Essays (1904), "Priest and Prophet" (1893), p. 132

“Life has its own hidden forces which you can only discover by living.”

“Another force driving progressive evolution is the so-called "arms-race."”
Prey animals evolve faster running speeds because predators do. Consequently predators have to evolve even faster running speeds, and so on, in an escalating spiral. Such arms races probably account for the spectacularly advanced engineering of eyes, ears, brains, bat "radar" and all the other high-tech weaponry that animals display.
The Evolutionary Future of Man (1993)