“Some day, the world will discover that, without thought, there can be no love.”

"The Evolution of Chastity" (February 1934), as translated in Toward the Future (1975) edited by by René Hague, who also suggests "space" as an alternate translation of "the ether."
Variants:
"One day after mastering the winds, the waves, the tides and gravity" — after all the scientific and technological achievements — "we shall harness for God the energies of love. And then, for the second time in the history of the world, man will have discovered fire."
As quoted by R. Sargent Shriver, Jr. in his speech accepting the nomination as the Democratic candidate for vice president, in Washington, D. C. (8 August 1972); this has sometimes been published as if Shriver's interjection "after all the scientific and technological achievements" were part of the original statement, as in The New York Times (9 August 1972), p. 18
What paralyzes life is lack of faith and lack of audacity. The difficulty lies not in solving problems but identifying them.
As translated in The The Ignatian Tradition (2009) edited by Kevin F. Burke, Eileen Burke-Sullivan and Phyllis Zagano, p. 86
Love is the only force which can make things one without destroying them. … Some day, after mastering the winds, the waves, the tides and gravity, we shall harness for God the energies of love, and then, for the second time in the history of the world, man will have discovered fire.
As quoted in Seed Sown : Theme and Reflections on the Sunday Lectionary Reading (1996) by Jay Cormier, p. 33
The day will come when, after harnessing space, the winds, the tides, gravitation, we shall harness for God the energies of love. And, on that day, for the second time in the history of the world, humanity will have discovered fire.
As quoted in Fire of Love : Encountering the Holy Spirit (2006) by Donald Goergen, p. 92
The day will come when, after harnessing space, the winds, the tides, gravitation, we shall harness for God the energies of love. And, on that day, for the second time in the history of the world, man will have discovered fire.
As quoted in Read for the Cure (2007) by Eileen Fanning, p. v
Variant: Someday, after mastering the winds, the waves, the tides and gravity, we shall harness for God the energies of love, and then, for a second time in the history of the world, man will have discovered fire.
Context: What paralyzes life is lack of faith and lack of audacity. The difficulty lies not in solving problems but expressing them. And so we cannot avoid this conclusion: it is biologically evident that to gain control of passion and so make it serve spirit must be a condition of progress. Sooner or later, then, the world will brush aside our incredulity and take this step : because whatever is the more true comes out into the open, and whatever is better is ultimately realized. The day will come when, after harnessing the ether, the winds, the tides, gravitation, we shall harness for God the energies of love. And, on that day, for the second time in the history of the world, man will have discovered fire.

1950s, Loving Your Enemies (November 1957)
Variant: We must discover the power of love, the power, the redemptive power of love. And when we discover that we will be able to make of this old world a new world. We will be able to make men better. Love is the only way.
Context: But there is another way. And that is to organize mass non-violent resistance based on the principle of love. It seems to me that this is the only way as our eyes look to the future. As we look out across the years and across the generations, let us develop and move right here. We must discover the power of love, the power, the redemptive power of love. And when we discover that we will be able to make of this old world a new world. We will be able to make men better. Love is the only way.

Source: Unweaving the Rainbow: Science, Delusion and the Appetite for Wonder

Source: Devil at My Heels

The Elements of Morality, Book 1, ch. 1. (1845).

Source: Stray Birds