"Nothing is more despicable than the old age of a passionate man. When the vigour of youth fails him, and his amusements pall with frequent repetition, his occasional rage sinks by decay of strength into peevishness; that peevishness, for want of novelty and variety, becomes habitual; the world falls off from around him, and he is left, as Homer expresses it, to devour his own heart in solitude and contempt."

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What does Reverence for Life say abut the relations between [humanity] and the animal world? Whenever I injury any kind of life I must be quite certain that it is necessary. I must never go beyond the unavoidable, not even in apparently insignificant things. The farmer who has mowed down a thousand flowers in his meadow in order to feed his cows must be careful on his way home not to strike the head off a single flower by the side of the road in idle amusement, for he thereby infringes on the law of life without being under the pressure of necessity.

— Albert Schweitzer