“It was the elision of the weaker element — the survival of the fittest; and some, indeed very many, mothers must lose their sons that way.”

Source: Mars and its Canals (1906), Chapter XXXII, Conclusion
Context: War is a survival among us from savage times and affects now chiefly the boyish and unthinking element of the nation. The wisest realize that there are better ways for practicing heroism and other and more certain ends of insuring the survival of the fittest. It is something a people outgrow. But whether they consciously practice peace or not, nature in its evolution eventually practices it for them, and after enough of the inhabitants of a globe have killed each other off, the remainder must find it more advantageous to work together for the common good.

Source: Manhood of Humanity (1921), p. 136. Chapter: Capitalistic Era.
Context: Such as contribute most to human progress and human enlightenment — men like Gutenberg, Copernicus, Newton, Leibnitz, Watts, Franklin, Mendeleieff, Pasteur, Sklodowska-Curie, Edison, Steinmetz, Loeb, Dewey, Keyser, Whitehead, Russell, Poincaré, William Benjamin Smith, Gibbs, Einstein, and many others — consume no more bread than the simplest of their fellow mortals. Indeed such men are often in want. How many a genius has perished inarticulate because unable to stand the strain of social conditions where animal standards prevail and "survival of the fittest" means, not survival of the "fittest in time-binding capacity," but survival of the strongest in ruthlessness and guile — in space-binding competition!

Could You Be Loved
Uprising (1979)

As quoted Clement of Alexandria, Stromata, V, 140, 6 (Fragment 35)

As "Trudy"
Contributions of Jane Wagner, The Search for Signs of Intelligent Life in the Universe (1985)

The Great Illusion (1910)

Source: The Selfish Gene (1976, 1989), Ch. 2. The replicators

Source: I Know This Much Is True

Source: What Is This Thing Called Science? (Third Edition; 1999), Chapter 5, Introducing falsification, p. 60.