Boundaries - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 199

of good design are crafted from materials that preserve the stamp of time's
arrow. "Fishness" is a timeless principle of good design; Ichthyosaurus is a
particular reptile in a particular time and place. Two world views, eternal
metaphors, jockey for recognition within every organism—receiving special
attention according to the aims and interests of students: homology and
analogy; history and optimality; transformation and immanence.
How, then, can we judge the interaction of time's arrow and time's cycle within
each object? I can specify two incorrect approaches: we must not seek one in
order to exclude the other (as Hutton did in denying history, before Lyell
expanded his vision to become a historian of time's cycle); but neither should
we espouse a form of wishy-washy pluralism that melds the end-members into
an undefined middle and loses the essence of each vision—the uniqueness of
history, and the immanence of law. Arrows and cycles, after all, are only
categories of our invention, devised for
Figure 5.8
Time's arrow of homology and time's cycle of analogy combine to produce this
Ichthyosaurus. The dorsal and caudal fins are convergent (with uncanny
precision) upon similar structures in fishes, but have evolved independently in
this descendant of terrestrial reptiles. Yet the signs of reptilian origin
(homology) are evident throughout the skeleton, particularly in the finger
bones enclosed within the fins.