“The invention and spread of contraceptives is the proximate cause of our changing morals.”
The old moral code restricted sexual experience to marriage, because copulation could not be effectively separated from parentage, and parentage could be made responsible only through marriage. But to-day the dissociation of sex from reproduction has created a situation unforeseen by our fathers. All the relations of men and women are being changed by this one factor; and the moral code of the future will have to take account of these new facilities which invention has placed at the service of ancient desires.
Our Changing Morals, in The Mansions of Philosophy: A Survey of Human Life and Destiny, (1929), Simon and Schuster, New York, ch. 5. p. 119.
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Will Durant 85
American historian, philosopher and writer 1885–1981Related quotes

Connections (1979), 10 - Yesterday, Tomorrow and You
Source: Star Maker (1937), Chapter III: The Other Earth; 2. A Busy World (p. 33)

The Redempton of the Robot (1969)
Other Quotes

Speech http://hansard.millbanksystems.com/commons/1924/jun/18/imperial-preference in the House of Commons (18 June 1924).
1924

these, though but the feeble steps of an understanding limited in its faculties and its materials of knowledge, are of more avail than the ambitious attempt to arrive at a certainty unattainable on the ground of natural religion. And as these were the most ancient, so are they still the most solid foundations, Revelation being set apart, of the belief that the course of this world is not abandoned to chance and inexorable fate.
Also found in Boole, George (1851). The claims of science, especially as founded in its relations to human nature; a lecture, Volume 15. p. 24
Source: 1850s, An Investigation of the Laws of Thought (1854), p. 217: Ch. 13. Clarke and Spinoza : Concluding remarks of the chapter

As quoted in Women on War : Essential Voices for the Nuclear Age (1988), by Daniela Gioseffi, p. 103
Variant: A pebble cast into a pond causes ripples that spread in all directions. Each one of our thoughts, words and deeds is like that. No one has a right to sit down and feel hopeless. There's too much work to do.
As quoted in Singing the Living Tradition (1993) by the Unitarian Universalist Association, p. 560
Context: What I want to bring out is how a pebble cast into a pond causes ripples that spread in all directions. And each one of our thoughts, words and deeds is like that. Going to jail for distributing leaflets advocating war tax refusal causes a ripple of thought, of conscience among us all. And of remembrance too. …. There may be ever improving standards of living in the U. S., with every worker eventually owning his own home and driving his own car; but our modern economy is based on preparation for war. … The absolutist begins a work, others take it up and try to spread it. Our problems stem from our acceptance of this filthy, rotten system.

2000s, 2003, Mission Accomplished (May 2003)