struggling with the world 139problems of physics rather than from its revolutionary past. Suppose
that in the attempt to make better sense of its discovery that the uni-
verse has a history than it has made so far, physics in its cosmological
applications were to cast off four intimately related sets of assumptions
that have thus far shaped its course.*
Th e fi rst set of assumptions is the form of explanation that became
canonical in physics ever since the time of Galileo and Newton. It is
what I earlier called the Newtonian paradigm: we distinguish a con-
fi guration space— a part of the universe— in which immutable laws
govern the movement or change of certain phenomena from the stipu-
lated, unexplained initial conditions shaping that confi guration space.
What is merely stipulated for the purpose of one set of explanations
can, however, become the subject matter to be explained in another set.
Physicists and cosmologists have regularly extrapolated the Newtonian
paradigm to the explanation of some aspect of the history of the uni-
verse. Such an extrapolation amounts to a cosmological fallacy: the
distinction between a confi guration space and initial conditions breaks
down when the subject matter is the universe and its history rather
than some part of nature.
A second set of assumptions is the generalization in physics and cos-
mology of the features of the cooled- down, mature universe: moderate
degrees of temperature and energy; limited susceptibility to change in
the succession to present states of aff airs; the or ga ni za tion of nature
into a diff erentiated structure, defi ned by distinct components; and
stable laws of nature, clearly distinct from the states of aff airs that they
govern. Yet, given what we now know about the early history of the
universe, there may have been a time when nature showed a radically
diff erent face, free of all these traits. Our conception of the workings of
nature, and our explanatory procedures, must be able to encompass
both faces of nature.
A third set of assumptions clings to the idea of unchanging laws of na-
ture. Th ese eff ective laws, and the yet more general principles exemplifi ed
in their operation, serve, according to the reigning orthodoxy in natural
* For a full account of the reasons to reject them, as well as of the consequences of do-
ing so, see again Th e Singular Universe and the Reality of Time.