I understand by an argument from design one which argues from some general pattern of order in the universe or provision for the needs of conscious beings to a God responsible for these phenomena. An argument from a general pattern of order I shall call a teleological argument. In the definition of ‘teleological argument’ I emphasize the words ‘general pattern’; I shall not count an argument to the existence of God from some particular pattern of order manifested on a unique occasion as a teleological argument.

Suppose we went on a mission to Mars, and found a domed structure in which everything was set up just right for life to exist. The temperature, for example, was set around 70^o F and the humidity was at 50%; moreover, there was an oxygen recycling system, an energy gathering system, and a whole system for the production of food. Put simply, the domed structure appeared to be a fully functioning biosphere. What conclusion would we draw from finding this structure? Would we draw the conclusion that it just happened to form by chance? Certainly not. Instead, we would unanimously conclude that it was designed by some intelligent being. Why would we draw this conclusion? Because an intelligent designer appears to be the only plausible explanation for the existence of the structure. That is, the only alternative explanation we can think of — that the structure was formed by some natural process — seems extremely unlikely. Of course, it is possible that, for example, through some volcanic eruption various metals and other compounds could have formed, and then separated out in just the right way to produce the "biosphere," but such a scenario strikes us as extraordinarily unlikely, thus making this alternative explanation unbelievable.

Both astrophysicists and microphysicists have lately been discovering that the series of events that produced our universe had to happen in a rather precise way—at least, they had to happen that way if they were to produce life as we know it. Some might find this fact unremarkable. After all, we are here, and it is hardly surprising that the universe is of such kind as to have produced us. It is simply a tautology to say that people who find themselves in a universe live in a universe where human life is possible. Nevertheless, given the innumerable other things that could have happened, we have reason to be impressed by the astonishing fact of our existence. Like the man who survives execution by a 1,000-gun firing squad, we are entitled to suspect that there is some reason we are here, that perhaps there is a Friend behind the blast.