“Whether across death's threshold we step from life to life, or whether we go whence we shall not return, even to the land of darkness, as darkness itself, he cannot tell.”
Science and Immortality (1904)
Context: Though his philosophy finds nothing to support it, at least from the standpoint of Terence the scientific student should be ready to acknowledge the value of a belief in a hereafter as an asset in human life. In the presence of so many mysteries which have been unveiled, in the presence of so many yet unsolved, he cannot be dogmatic and deny the possibility of a future state; and however distressing such a negative attitude of mind to the Teresian, like Pyrrho, he will ask to be left, reserving his judgement, but still inquiring. He will recognize that amid the turbid ebb and flow of human misery, a belief in the resurrection of the dead and the life of the world to come is the rock of safety to which many of the noblest of his fellows have clung; he will gratefully accept the incalculable comfort of such a belief to those sorrowing for precious friends hid in death's dateless night; he will acknowledge with gratitude and reverence the service to humanity of the great souls who have departed this life in a sure and certain hope but this is all. Whether across death's threshold we step from life to life, or whether we go whence we shall not return, even to the land of darkness, as darkness itself, he cannot tell.
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William Osler 50
Canadian pathologist, physician, educator, bibliophile, his… 1849–1919Related quotes

"Remarks in Newport at the Australian Ambassador's Dinner for the America's Cup Crews (383)" (14 September 1962) http://www.jfklibrary.org/Research/Research-Aids/Ready-Reference/JFK-Quotations.aspx<!-- Public Papers of the President: John F. Kennedy, 1962 -->
1962
Context: I really don't know why it is that all of us are so committed to the sea, except I think it's because in addition to the fact that the sea changes, and the light changes, and ships change, it's because we all came from the sea. And it is an interesting biological fact that all of us have, in our veins the exact same percentage of salt in our blood that exists in the ocean, and, therefore, we have salt in our blood, in our sweat, in our tears. We are tied to the ocean. And when we go back to the sea — whether it is to sail or to watch it — we are going back from whence we came.

“We come from a dark abyss, we end in a dark abyss, and we call the luminous interval life.”
The Saviors of God (1923)
Context: We come from a dark abyss, we end in a dark abyss, and we call the luminous interval life. As soon as we are born the return begins, at once the setting forth and the coming back; we die in every moment. Because of this many have cried out: The goal of life is death! But as soon as we are born we begin the struggle to create, to compose, to turn matter into life; we are born in every moment. Because of this many have cried out: The goal of ephemeral life is immortality! In the temporary living organism these two streams collide … both opposing forces are holy. It is our duty, therefore, to grasp that vision which can embrace and harmonize these two enormous, timeless, and indestructible forces, and with this vision to modulate our thinking and our action.

Quoted in "The Columbia Dictionary of Quotations" - Page 446 - by Robert Andrews - Reference - 1993.

“Now he goes along the dark road, thither whence they say no one returns.”
Qui nunc it per iter tenebricosum
illuc, unde negant redire quemquam.
III, lines 11–12
Carmina

The statement "The future of all life, including our own, depends on our mindful steps." and much of the theme of this essay also occur later in his writings, including The World We Have : A Buddhist Approach to Peace and Ecology (2008), Ch. 1 : The Bells of Mindfulness, p. 3
The Sun My Heart (1996)
Context: All life is impermanent. We are all children of the Earth, and, at some time, she will take us back to herself again. We are continually arising from Mother Earth, being nurtured by her, and then returning to her. Like us, plants are born, live for a period of time, and then return to the Earth. When they decompose, they fertilize our gardens. Living vegetables and decomposing vegetables are part of the same reality. Without one, the other cannot be. After six months, compost becomes fresh vegetables again. Plants and the Earth rely on each other. Whether the Earth is fresh, beautiful, and green, or arid and parched depends on the plants.
It also depends on us. Our way of walking on the Earth has a great influence on animals and plants. We have killed so many animals and plants and destroyed their environments. Many are now extinct. In turn, our environment is now harming us. We are like sleepwalkers, not knowing what we are doing or where we are heading. Whether we can wake up or not depends on whether we can walk mindfully on our Mother Earth. The future of all life, including our own, depends on our mindful steps.

1963, Civil Rights Address