overcoming the world 65Th e strong point of this radical version of the metaphysics of the re-
ality of the world is its notion of the impermanence of all types of be-
ing. Its weak point is its denial of the reality of time. Impermanence
with time affi rmed means something very diff erent from imperma-
nence with time denied, and has very diff erent implications for the
conduct of life and the signifi cance of history. Th ese contrasts come
more clearly into focus when we consider them in relation to the dis-
coveries and disputes of contemporary cosmology.*
Th ere is much in what science has discovered about the universe and
its evolution to suggest the impermanence of the structural distinctions
that we observe in nature. We are familiar in the life and earth sciences
with the principle of the mutability of types: there is, in the history of
the earth and of life on earth, no permanent typology of natural kinds,
whether the kinds of being are living or lifeless. Every part of this ty-
pology is historical; its content changes, albeit discontinuously in time.
Th e types of being change. So does the character of the ways in
which one natural kind diff ers from another. An igneous rock does not
diff er from a sedimentary rock in the same way, or in the same sense,
that one animal species diff ers from another.
Th e mutability of types is in turn connected with a principle of hys-
teresis or path de pen den cy. Th e history of mutable types is the con-
comitant product of many loosely connected sequences of change that
cannot persuasively be reduced to one another or inferred from a
higher- order explanation: for instance, in Darwinian evolution the re-
lation among the distinct infl uences of natural selection, of the struc-
tural constraints and opportunities created by an established repertory
of body types, and of the historical movement and separation of land
masses, studied by plate tectonics.
Th e larger meaning of the principles of path de pen den cy and of the
mutability of types becomes clear in the light of a third principle of
* Lee Smolin and I develop these ideas in Th e Singular Universe and the Reality of
Time, 2014. If the claims of that essay in natural philosophy are well founded, noth-
ing in the entire argument of this volume, or in the philosophical program that it
shares with my book Th e Self Awakened, contradicts what science has to teach us
about how nature works: not at least if we learn to interpret the fi ndings of science
without the blinkers of unwarranted metaphysical prejudice.