 agere sequitur esse: Action follows upon essence. We know what a thing is by what it does, and therefore has the power to do. The nature (constitution, composition, inherent order) of a being is an interior principle or source of action. But some actions are higher in themselves than others, and they, too, require explanation in a theory of evolution.
The eye is the organ of sight. But seeing is an action that is new, distinct in kind, and does something that is not merely more than earlier organisms could do. It is something on a totally different and higher level of action, therefore of being. Can it be understood or explained simply in terms of the evolution of the organ?
I remember a Catholic of liberal views once asking me whether, if a television camera had been present at the resurrection of Christ it would have seen anything. There are several answers to that question, but the one that is relevant here is that a television camera does not see. It receives an image carried by light and transmits it to audiences around the globe. But the machine, being a machine, does not see. Only living, bodily creatures do that. They cannot do it without eyes and light to see by. But is the act of seeing reducible to the necessary conditions of sight? Or is it a reality for which they alone are not a sufficient explanation?
Your materialist will of course say that the necessary conditions are a sufficient explanation of sight; given the evolution of organs that make sight possible, living beings will see. Implicit in that answer, however, is a denial that evolution is a rising curve. There are no actions that lie beyond the capacity of purposelessly evolving matter. The movement is from simplicity to growing complexity, nothing more. Complexity makes new actions possible, but since effects do not exceed causes, they are actions that matter was always capable of producing, and they do not attain any higher level of being or action. All that was lacking was the development of the necessary conditions of the actions, which remain essentially on the same level.
In reply we may remark that while great oaks from little acorns grow, great mountains do not grow from little grains of rock that organize themselves from within. Self-replicating molecules are the elementary stuff of life; non-self-replicating ones are not alive. Plants reproduce themselves but feel no pain; animals both reproduce and feel pain. Higher animals are aware of an outer world through such senses as they have; a virus presumably is not, although it is a living organism. There is such a thing as animal intelligence, but it has several observable levels. Soaring above them all is human intelligence. All of these differences would seem to require some explanation other than the chance formation of the necessary organs.
The once famous Lucy, a chimpanzee, was able to order items of food and drink by punching buttons on an electronic board, but that is as far as she went. I have read that the differences between the chromosomes of chimpanzees and humans amount to a variation of only 1.9 percent. That certainly suggests a common ancestry of ourselves and our very remote cousins, the chimpanzees. It does not suggest that the difference between the two species is a slight one.
It is fashionable in certain circles to decry as arrogant the claim that man is superior to beasts. Stephen Jay Gould has said, "it is so arrogant of us to think of dinosaurs as unsuccessful because they are dead." They lasted far longer on this earth than we have so far done, he asserted, and we don't know how long we shall last. This makes sense if, but only if, success is measured solely in terms of longevity.
But there may be other criteria of success. Off the top of the head one can think of Mozart and Beethoven; Praxiteles and Michelangelo; Sophocles and Shakespeare; Plato, Aristotle, Aquinas (and let us throw in Hegel); Moses, Isaiah, and Jesus, not to mention the great names of non-Western cultures. No dinosaurs of which we have records rivaled them. The difference between men and dinosaurs