At sunset there flashed upon my mind, the phrase :

 “Ehrfurcht vor dem Leben” (“reverence for life”).”

After great mental struggle Albert Schweitzer had what can be called his epiphany:

Late on the third day, at the very moment when, at sunset, we were making our way through a herd of hippopotamuses, there flashed upon my mind, unforeseen and unsought, the phrase : “Ehrfurcht vor dem Leben” (“reverence for life”). The iron door had yielded. The path in the thicket had become visible.”
— Albert Schweitzer

"Reverence for Life says that the only thing we are really sure of is that we live and want to go on living. This is something that we share with everything else that lives, from elephants to blades of grass – and, of course, every human being. So we are brothers and sisters to all living things, and owe to all of them the same care and respect, that we wish for ourselves.”
— James Brabazon

"The most immediate fact of man’s consciousness is the assertion ‘I am life that wills to live in the midst of life that wills to live’,"
—Albert Schweitzer


"Affirmation of life is the spiritual act by which man ceases to live thoughtlessly and begins to devote himself to his life with reverence in order to give it true value. To affirm life is to deepen, to make more inward, and to exalt the will to live.

At the same time the man who has become a thinking being feels a compulsion to give to every will to live the same reverence for life that he gives to his own.[....] This is the absolute, fundamental principle of ethics, and is a fundamental postulate of thought.”
— Albert Schweitzer


“By itself, the affirmation of life can only produce a partial and imperfect civilization. Only if it turns inward and becomes ethical can the will to progress attain the ability to distinguish the valuable from the worthless. We must therefore strive for a civilization that is not based on the accretion of science and power alone, but which cares most of all for the spiritual and ethical development of the individual and of humankind.”
—Albert Schweitzer


“Standing, as all living beings are, before this dilemma of the will to live, a person is constantly forced to preserve his own life and life in general only at the cost of other life. If he has been touched by the ethic of reverence for life, he injures and destroys life only under a necessity he cannot avoid, and never from thoughtlessness.”
—Albert Schweitzer