“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!”

Source: On Aggression (1963), Ch. XII : On the Virtue of Scientific Humility
Context: 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!