Charles Lyell, Historian of Time's Cycle - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 172

plain the same phenomenon of progress as a consequence of evolution. A key
passage reveals that Lyell's distress centered on the fact of progress, and that
he viewed evolution as a more acceptable explanation for life's advance than
old-fashioned progressionism in its unvarnished form:
There is but little difference between the out and out progressionist and
Lamarck, for in the one case some unknown modus operandi called creation
is introduced and admitted to be governed by a law causing progressive
development and by the other an extension or multiplication by Time of the
variety-making power is adopted instead of the unknown process called
Creation. It is the theory of a regular series of progressively improved beings
ending with Man as part of the same, which is the truly startling conclusion
destined, if established, to overturn and subvert received theological dogmas
and philosophical reveries quite as much as Transmutation . . . There seems
less to choose between the rival hypotheses [evolution and progressionism]
than is usually imagined, (in Wilson, 1970, 222-223)
I regard this last statement (repeated with little variation many times
throughout the journals) as the key to Lyell's conversion. He does not accept
evolution because facts proclaim it—for he finds little to choose between
evolution and progressionism as an explanation for the phenomenon of
improvement, now reluctantly admitted. Why, then, prefer evolution?
Lyell's answer seems clear in the journals: evolution is the fallback position
of minimal retreat from the rest of uniformity, once life's progress be
admitted. If progressionism be embraced, the uniformity of rate will be
threatened as well because mass extinction had long been the foundation of
progressionist mechanics. Even the uniformity of law might be challenged, if
an essentially mysterious process of creation be advocated as the cause of
origin (remember that Lyell had never been a creationist, but agnostic about
modes of origin for new species). And what about the uniformity of