The Anthropic Principle

The Anthropic Principle has had a long and sordid history among cosmologists and others.  In essence, the principle asserts that the fine-tuning of the physical constants that allow for the formation of conscious life requires some sort of explanation.  As an example, some physicists try to argue for the existence of multiple universes in order to account for the precise values of physical laws, like the cosmological constant.  However, this reasoning seems to be a bit flawed.

Many writers who invoke the Anthropic Principle speak of the principle as if it somehow demonstrates some sort of strange fact about the universe.  But the Anthropic Principle doesn’t really demonstrate anything.  It merely presents a problem, not an explanation.  The principle can’t be used to justify a hypothesis if there is no other additional evidence for the hypothesis in question.  As such, I don’t quite understand the fascination with the Anthropic Principle exhibited by many physicists.

Consider someone who has won a lottery.  Such an event is quite improbable.  According to anthropic reasoning, this improbable event would require some sort of explanation.  Suppose a cosmologist argued that he could explain this event by invoking multiple universes where the person plays the lottery.  The person loses in most of the universes, but happens to have won in our own.  In this sense, the improbability is explained away.  The cosmologist can further argue that the mathematical model of this multiverse is consistent and trumpet this as some saving grace of his hypothesis.  But in the end, if there is no additional evidence of these multiple universes, mere mathematical consistency is not enough to support such a hypothesis, nor is the improbability of winning the lottery reason enough to assert such a bizarre hypothesis.

The problem with such anthropic reasoning, as I see it, is that there are a variety of other potential explanations, and without additional evidentiary support they can’t be ruled out.  Beyond that, it doesn’t even seem as if improbable events necessarily require explanations beyond chance.  By definition, even very unlikely events can still occur, as they are only unlikely, not impossible.  Aside from chance occurences and multiverses, there are a number of other possible explanations, ranging from benevolent deities creating things in this way to “evolutionary” mechanisms that select for universes that promote life or perhaps universe characteristics that correlate with the formation of life.  Without any sort of additional evidence for benevolent deities, or multiple universes, or evolutionary selection mechanisms for universes, though, such explanations are only baseless conjecture.  I don’t think it is enough for String Theorists to talk as if the precise values of the physical constants, in tandem with the mathematical consistency of their models, is evidence for such a conjecture.

Of course, I am not terribly well-read on the subject, and if anyone has any resources that present any additional evidence for such explanations, I’d gladly look into it.  But it seems to me that the Anthropic Principle is highly questionable as a “scientific” principle.