Explanations of Life
Suppose we encounter life forms on another planet unrelated to ours and possibly quite unlike ours. Still, there is evident adaptive complexity, so that the laws of physics and chance cannot explain what we observe. What possible explanation might be given for this complexity? How might it have come to be?
One possibility is intelligent design—not by God, to be sure, but by scientifically advanced aliens. These organisms might have been synthesized on a Life Production Machine. They are in effect artifacts of another civilization, so the explanation of their existence matches the explanation for the existence of artifacts in our civilization: intentional intelligent design. We can’t rule this explanation out; it is a matter of empirical fact whether it is true (just as it is for life on earth). We might well gather further information that rules out the hypothesis (there is no such advanced civilization in the vicinity), but as a matter of principle the hypothesis is a theoretical possibility—it cannot be excluded a priori. Alternatively, the life forms might have arisen by ordinary natural selection with no intelligent intervention. But there are also mixed cases: the organisms might have been subjected to guided breeding after a period of natural evolution, or they might be genetically engineered and then left to natural selection. Conceivably they might be selectively bred from an initial batch of bacteria, so partly the result of natural design and partly of intelligent design. There is an indefinite range of possible combinations of natural evolution and guided evolution, varying between species and planetary fauna—for instance, the mammals have been left to natural selection while the reptiles have been intensively bred for intelligence or strength. Maybe elsewhere in the universe all the possibilities have been tried—as is partially the case on earth where humans have artificially bred certain species but not others.
The traditional theoretical dichotomy between intelligent design and natural selection may be quite parochial where advanced civilizations have developed, because there is ample scope for partial intervention into the process of generating life. Selective breeding and genetic engineering can certainly speed up the evolutionary process considerably, taking decades to achieve what natural selection would take millions of years to achieve. When intelligent life forms take evolution into their own hands the sky is the limit. Naturally evolved life might be the most primitive form of life, vastly outclassed by the kind of life created by life itself, i.e. designed by life forms with the intelligence to change the course of evolution. No need to wait for that lucky chance mutation; just create whatever mutation looks promising and then subject the result to rigorous test. Just as bacteria look very primitive in the light of later evolutionary developments, so naturally evolved life might look very primitive compared to the kind of life that intelligent designers can contrive. If the secret to the origin of life is ever discovered, it could be used to re-start the entire process, producing untold wonders by creative intervention. All of life could come to be intelligently designed.
Interestingly, the possibility of intelligent design depends upon antecedent natural design: not every life form in history could be the result of intelligent design, since an intelligent life form has to come from somewhere. No universe could create intelligent life ab initio: the long and painful process of natural selection has to create the first form of intelligence, since intelligence cannot depend upon other intelligence all the way down. But once a form of intelligence has evolved that is capable of selective breeding and guided evolution, it can produce new life forms without reliance on the old machinery of blind random mutation and natural selection. Then the explanation for the design of organisms will involve intelligent design not natural design. Most of the life in the universe might be of this kind: whole galaxies could be inhabited by intelligently designed organisms. Geological time is vast but cosmological time is much vaster, so the possibility of intelligently designed life coming to dominate the universe can’t be ruled out. We might be just at the beginning of the history of life—the short initial period in which life evolved naturally. Already we are beginning to change the course of evolution; genetic engineering could accelerate this process enormously. Other intelligent species elsewhere might be much further along in imposing their will on nature.
If a Charles Darwin is born on a planet that has been subject to intelligent design, he will hit upon the correct theory of evolution for that planet, namely evolution by intelligent design.  Maybe life was seeded naturally by the accidental arrival of bacteria, but then intelligent creatures stepped in to guide the course of evolution, creating whatever organisms took their fancy. A rival theorist who hypothesized natural selection as the explanation would be mistaken; there was, on this planet, an intelligent designer responsible for the adaptive complexity on display. Natural evolution could have ended millions of years ago, with all life now the result of intentional intervention. The traditional Darwinian theory used to be true, but it is no more: everything is now carefully monitored and cultivated. This is what is taught in biology classes these days, and it is entirely correct. All genetic alteration is brought about by scientific intervention, so that nothing is left to chance; then certain strains are chosen for reproduction and others rejected. It is as if the old religious creationist story were true, only it is not a divine being calling the shots but a super-alien. On our planet now Darwin’s theory is the true theory, but on other planets the theory of intelligent design may be the true theory (and may come to be the true theory on our planet). There might come a time when none of the species inhabiting the galaxies evolved by natural selection. That was just the early phase in the history of life, and destined to be superseded by intelligent design. Evolution will cease to be blind. 
 His book On the Origin of Species defends the view that all life results from the intentional actions of a mighty intelligent designer. This Darwin might not know the identity of the designer—that was not discovered until space travel became a possibility centuries later—but he was brilliant enough to see that no other explanation could be true given the facts. Organisms were just too well designed for this to be a matter of blind variation and mindless selection! He considered the alternative theory but found it wanting—and he was entirely right in his conclusions and reasoning.
 Just to be scrupulously clear, this essay is not intended to provide succor for creationists about life as it evolved on planet Earth; I am speaking of imaginary planets and imaginary ways of shaping life.