Geology Reference
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concentrated in episodes of mass death or radiation, but are distributed
evenly through space and time—another dynamic steady state as
introductions are balanced by removals. Moreover, the timing of
introductions displays no progress in organization or complexity, no advance
through the chain of being. Lyell argued (see pages 137-142) that
appearances of progress in stratigraphic origins (from fish to reptile to
mammal to human in the history of vertebrates, for example) were illusory.
He believed that mammals had lived during earliest Paleozoic times and that
future exploration would recover their fossil remains from these ancient
rocks.
Lyell's extension of the fourth uniformity to life strikes many people as
intensely puzzling. They can appreciate the force behind a claim for
uniformity of state in the physical world, but surely we know that life must
change in a progressive manner. Yet, for Lyell, the link of life to the physical
world was direct and necessary. He held that species arose (whether by God's
hand or by some unknown secondary cause) in perfect adaptation to physical
surroundings. Any progressive change in life's state could only mirror a
corresponding alteration in the physical environment. Since uniformity of
state pervades climate and geography, life must also participate in the
nondirectional dance.
Lyell defended uniformity of state with the same devices of rhetoric that he
had applied to gradualism—he conflated this testable and controversial
theory about the nature of things with methodological canons that all
scientists accept, thereby attempting to secure an a priori status for time's
cycle as a necessary component of rationality itself.
Consider two examples. Lyell often argued against directional theories not by
citing contrary evidence, but by holding that their claims for a different earth
in the past could not be rendered accessible to inquiry or even made
intelligible. He refutes the old Neptunian theory of original deposition from a
universal ocean not with stratigraphic evidence, but in principle because it
advocates an ancient earth different in state from our own:
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