Schweitzer's worldview was based on his idea of
Reverence for Life ("
Ehrfurcht vor dem Leben"), which he believed to be his greatest single contribution to humankind. His view was that
Western civilization was in decay because of gradually abandoning its
ethical foundations - those of affirmation of life.
It was his firm conviction that the respect for life is the highest principle. In a similar kind of exaltation of life to that of
Friedrich Nietzsche, a recently influential philosopher of the time, Schweitzer admittedly followed the same line as that of the Russian
Leo Tolstoy. Some people in his days compared his philosophy with that of
Francis of Assisi, a comparison he did not contest. In his book
The Philosophy of Civilization (all quotes in this section from chapter 26), he wrote:
:
"True philosophy must start from the most immediate and comprehensive fact of consciousness: 'I am life that wants to live, in the midst of life that wants to live'."
Life and love in his view are based on, and follow out of the same principle: respect for every manifestation of life, and a personal, spiritual relationship towards the universe. Ethics, according to Schweitzer, consists in the
compulsion to show toward the will-to-live of each and every being the same reverence as one does to one's own. Circumstances where we apparently fail to satisfy this compulsion should not lead us to defeatism, since the will-to-live renews itself again and again, as an outcome of an evolutionary necessity and a phenomenon with a spiritual dimension.
However, as Schweitzer himself pointed out, it is neither impossible nor difficult to spend one's life and not follow it: the history of world philosophies and religions shows many instances of denial of the principle of reverence for life. He points to the prevailing philosophy in the European Middle Ages, and the Indian
Brahminic philosophy as examples. Nevertheless, he contends that this kind of attitude lacks genuineness.
The will to live is naturally both parasitic and antagonistic towards other forms of life. Only in the thinking being has the will to live become conscious of other wills to live, and desirous of solidarity with it. This solidarity, however, cannot be brought about, because human life does not escape the puzzling and horrible circumstance that it must live at the cost of other life. But as an ethical being one strives to escape whenever possible from this necessity, and to put a stop to this disunion of the Will to live, so far as it is within one's power.
Schweitzer advocated the concept of reverence for life widely throughout his entire life. The historical
Enlightenment waned and corrupted itself, Schweitzer held, because it has not been well enough grounded in thought, but compulsively followed the ethical will-to-live. Hence, he looked forward to a renewed and more profound
Renaissance and Enlightenment of humanity (a view he expressed in the epilogue of his autobiography,
Out of My Life and Thought). Albert Schweitzer nourished hope in a humankind that is more profoundly aware of its position in the Universe. His optimism was based in "belief in truth". "The spirit generated by [conceiving of] truth is greater than the force of circumstances." He persistently emphasized the necessity to think, rather than merely acting on basis of passing impulses or by following the most widespread opinions.
:
"Never for a moment do we lay aside our mistrust of the ideals established by society, and of the convictions which are kept by it in circulation. We always know that society is full of folly and will deceive us in the matter of humanity. [...] humanity meaning consideration for the existence and the happiness of individual human beings."
Respect for life, resulting from contemplation on one's own conscious will to live, leads the individual to live in the service of other people and of every living creature. Schweitzer was much respected for putting his theory into practice in his own life. He was, for instance, a well-known
cat lover, who, although
left-handed, would write with his right hand rather than disturb the cat who would sleep on his left arm.