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Selection Effects

It would be evidence for a benevolent designer if life were better than could be expected on other grounds, including anthropic grounds. A certain capacity for joy would naturally evolve through natural selection, as an incentive to animals who need to eat and breed in order to pass on their genes. It may not be likely that evolution would produce animals who are fortunate enough to have the leisure and the ability to do science and think abstractly, but our sample of what is produced by evolution is very biased, by the fact that it is only in these fortunate cases that there is anyone thinking about cosmic design. Astronomers call this a selection effect. (Astronomers like Sandra Faber have to worry continually about selection effects of one sort or another.) The universe is very large, and it should be no surprise that, among the enormous number of planets that support only unintelligent life and the still vaster number that cannot support life at all, there is some tiny fraction on which there are living beings who are capable of thinking about the universe, as we are doing here. The real question is, whether life is better than would be expected from what we know about natural selection, taking into account the bias introduced by the fact that we are thinking about the problem.

This is a question that everyone will have to answer for themselves. Being a physicist is no help with questions like this, so I have to speak from my own experience. My life has been remarkably happy, probably in the upper 99.99 percentile of human happiness, but even I have seen a mother die painfully of cancer, a father's personality destroyed by Alzheimer's disease, and scores of second and third cousins murdered in the Holocaust. Signs of a benevolent designer are pretty well hidden.

The prevalence of evil and misery has always bothered those who believe in a benevolent and omnipotent God. Sometimes God is excused by pointing to the need for free will. Milton gives God this argument in Paradise Lost:

I formed them free, and free they must remain
Till they enthral themselves: I else must change
Their nature, and revoke the high decree
Unchangeable, eternal, which ordained
Their freedom; they themselves ordained their fall.

It seems a bit unfair to my relatives to be murdered in order to provide an opportunity for free will for Germans, but even putting that aside, how does free will account for cancer? Is it an opportunity of free will for tumors?

It is not necessary for me to argue here that the evil in the world proves that the universe is not designed, but only that there are no signs of benevolence that might have shown the hand of a designer. But in fact the perception that God cannot be benevolent is very old. Plays by Aeschylus and Euripides make a quite explicit statement that the Gods are selfish and cruel, though they expect better behavior from humans. God in the Old Testament demands of us that we be willing to sacrifice our children's lives at His orders, and the God of traditional Christianity and Islam damns us for eternity if we do not worship him in the right manner. Is this a nice way to behave? I know, I know, we are not supposed to judge God according to human standards, but you see the problem here: if we are not yet convinced of His existence, and are looking for signs of his benevolence, then what other standards can we use?

Contributed by: Dr. Steven Weinberg

Cosmic Questions

Was the Universe Designed? Topic Index

Selection Effects

No Exceptions to the Natural Order
The Persistent Questions: Why?
Fine Tuning
No Constructive Dialogue


Steven Weinberg

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The Anthropic Principle
The Argument from Design
Did the Universe Have a Beginning?
Was the Universe Designed?
Are we Alone?
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Hubble Deep Field Animation
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