The Argument from Design
The argument from design focuses on the fact that the universe is fit for human habitation. There are many ways that the universe might have been, the argument from design tells us—it might have had different laws of physics; it might have had a different arrangement of planets and stars; it might have begun with a bigger or a smaller big bang—and the vast majority of these universes would not have allowed for the existence of life. We are very fortunate indeed to have a universe that does.
The Universe Might Have Been Other Than It Is
Assume that modern science is correct in saying that the universe began with a big bang, that the universe came into existence with an explosion that sent pieces of matter flying in all directions at an enormous rate. The big bang might have been other than it was; it might have involved more or less matter, or have involved a larger or a smaller explosion, for example.
That the big bang occurred as it did was crucial for the development of life, because the rate of expansion of the universe, i.e. the speed at which the pieces of matter flew apart, had to fall within certain limits if life was to develop. Had the rate of expansion been too slow, then gravity would have pulled all of the matter back together again in a big crunch; there wouldn’t have been enough time for life to emerge.
Had the rate of expansion been too fast, then gravity wouldn’t have had a chance to pull any of the pieces of matter together, and planets, stars and even gases wouldn’t have been able to form; there wouldn’t have been anything for life to emerge on.
The rate of expansion following the big bang, of course, was just right to allow life to develop; if it weren’t then we wouldn’t be here now.
Had the Big Bang Been Different, the Universe Probably Wouldn’t Contain Life
That this was the case, though, was either an extraordinary fluke, or was intended by the big bang’s Creator. Had the rate of expansion been even fractionally slower—one part in a million million—then the big bang would have been followed by a big crunch before life could have developed. Had the rate of expansion been even fractionally faster—one part in a million—then stars and planets could not have formed. It is highly unlikely that a random big bang would be such as to allow life to develop, and therefore highly unlikely, according to the argument from design, that the big bang from which our universe was formed happened at random.
The fact that the universe is fit for life requires explanation, and an appeal to chance is no explanation at all. It is far more likely that the universe was initiated by a being that intended to create a universe that could support life. The fine-tuning of the universe for life can only be explained with reference to a Creator, as the result of intelligent design.
Other Examples of Fine-Tuning
The rate of the expansion of the universe following the big bang is just one instance of apparent design in the universe; other examples, like the strength of the weak force, the strength of the strong force, and isotropy, abound (for explanations and further examples see William Lane Craig’s The Teleological Argument and the Anthropic Principle).
Each example makes it less likely that the universe was created at random and more likely that it was designed by a Creator that takes an interest in humanity. Once all of this evidence is taken into account, the argument from design concludes, there can be no question as to whether the universe just happens to be fit for life or whether it was deliberately created that way; the universe clearly exhibits the marks of intelligent design.
What the Argument from Design Proves
As with the other arguments, there are a number of objections to the argument from design. If it is successful, however, then together with the ontological argument and the first cause argument it gives us proof that there is a perfect, necessary, and eternal Creator whose purpose in creating the universe was to bring about life. This would include most of the important elements of Christian theism; it would tell us that God exists, and what he is like, and that he created the universe with life in mind. It would not, however, tell us much about how we ought to respond.
The final argument, the moral argument, seeks to do this by demonstrating God’s authority and so showing that we ought to seek to live our lives in accordance with his plan.