"Nobody can seriously believe that free will means that it is left entirely to the will of the individual, as to an irresponsible tyrant, to do or not do whatever he pleases. Our freest will underlies strict moral laws, and one of the reasons for our longing for freedom is to prevent our obeying other laws than these. It is significant that the anguished feeling of not being free is never evoked by the realisation that our behaviour is just as firmly bound to moral laws as physiological processes are to physical ones. We are all agreed that the greatest and most precious freedom of man is identical with the moral laws within him. Increasing knowledge of the natural causes of his own behaviour can certainly increase a man's faculties and enable him to put his free will into action, but it can never diminish his will. If, in the impossible case of an utopian complete and ultimate success of causal analysis, man should ever achieve complete insight into the causality of earthly phenomena, including the workings of his own organism, he would not cease to have a will but it would be in perfect harmony with the incontrovertible lawfulness of the universe, the Weltvernunft of the Logos. This idea is foreign only to our present-day western thought; it was quite familiar to ancient Indian philosophy and to the mystics of the middle ages."

“The scientist who considers himself absolutely "objective" and believes that he can free himself from the compulsion of the "merely" subjective should try — only in imagination of course — to kill in succession a lettuce, a fly, a frog, a guineapig, a cat, a dog, and finally a chimpanzee. He will then be aware how increasingly difficult murder becomes as the victim's level of organisation rises. The degree of inhibition against killing each one of these beings is a very precise measure for the considerably different values that we cannot help attributing to lower and higher forms of life. To any man who finds it equally easy to chop up a live dog and a live lettuce I would recommend suicide at his earliest convenience!”

“All the advantages that man has gained from his ever-deepening understanding of the natural world that surrounds him, his technological, chemical and medical progress, all of which should seem to alleviate human suffering... tends instead to favor humanity's destruction.”

“We are the highest achievement reached so far by the great constructors of evolution. We are their "latest" but certainly not their last word. The scientist must not regard anything as absolute, not even the laws of pure reason. He must remain aware of the great fact, discovered by Heraclitus, that nothing whatever really remains the same even for one moment, but that everything is perpetually changing. To regard man, the most ephemeral and rapidly evolving of all species, as the final and unsurpassable achievement of creation, especially at his present-day particularly dangerous and disagreeable stage of development, is certainly the most arrogant and dangerous of all untenable doctrines. If I thought of man as the final image of God, I should not know what to think of God. But when I consider that our ancestors, at a time fairly recent in relation to the earth's history, were perfectly ordinary apes, closely related to chimpanzees, I see a glimmer of hope. It does not require very great optimism to assume that from us human beings something better and higher may evolve. Far from seeing in man the irrevocable and unsurpassable image of God, I assert – more modestly and, I believe, in greater awe of the Creation and its infinite possibilities – that the long-sought missing link between animals and the really humane being is ourselves!”

“Let us imagine that an absolutely unbiased investigator on another planet, perhaps on Mars, is examining human behavior on earth, with the aid of a telescope whose magnification is too small to enable him to discern individuals and follow their separate behavior, but large enough for him to observe occurrences such as migrations of peoples, wars, and similar great historical events. He would never gain the impression that human behavior was dictated by intelligence, still less by responsible morality.”

“The competition between human beings destroys with cold and diabolic brutality.... Under the pressure of this competitive fury we have not only forgotten what is useful to humanity as a whole, but even that which is good and advantageous to the individual.... One asks, which is more damaging to modern humanity: the thirst for money or consuming haste... in either case, fear plays a very important role: the fear of being overtaken by one's competitors, the fear of becoming poor, the fear of making wrong decisions or the fear of not being up to snuff.”

“A chapter from On Aggression”