Three Roads To Quantum Gravity

WHAT CHOOSES THE LAWS OF NATURE?
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anthropic principle. And if that is so, then those principles
have no logical force. Beyond this, the theory of cosmological
natural selection (as it is sometimes called) shows us that
physics can learn an important lesson from biology about
possible modes of scienti®c explanation. If we want to stick to
our principle that there is nothing outside the universe, then
we must reject any mode of explanation in which order is
imposed on the universe by an outside agency. Everything
about the universe must be explicable only in terms of how
the laws of physics have acted in it over the whole span of its
history.
Biologists have been facing up to this problem for more
than a century and a half, and they have understood the
power of different kinds of mechanism by which a system
may organize itself. These include natural selection, but that
is not the only possibility: other mechanisms of self-organization
have been discovered more recently. These include selforganized
critical phenomena, invented by Per Bak and
collaborators and studied by many people since. Other
mechanisms of self-organization have been studied by theoretical
biologists such as Stuart Kauffman and Harold Morowitz.
So there is no shortage of mechanisms for selforganization
that we could consider in this context. The
lesson is that if cosmology is to emerge as a true science, it
must suppress its instinct to explain things in terms of
outside agencies. It must seek to understand the universe on
its own terms, as a system that has formed itself over time, just
as the Earth's biosphere has formed itself over billions of
years, starting from a soup of chemical reactions.
It may seem fantastic to think of the universe as analogous
to a biological or ecological system, but these are the best
examples we have of the power of the processes of selforganization
to form a world of tremendous beauty and
complexity. If this view is to be taken seriously, we should
ask whether there is any evidence for it. Are there any aspects
of the universe and the laws that govern it that require
explanation in terms of mechanisms of self-organization? We
have already discussed one piece of evidence for this, which
is the anthropic observation: the apparently improbable