James Hutton's Theory of the Earth: A Machine without a History - Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time - page 95

tions. And these are the aspects of Hutton's thought that Playfair either soft-
pedals or presents in altered light. Playfair subtly "modernized" his friend,
and helped to set the basis of Hutton's legend by toning down his hostility to
history.
In one important change, Playfair largely excises Hutton's commitment to
final cause. He does not deny his friend's obsession with a style of science
already becoming archaic. Playfair even acknowledges the primacy of final
cause in Hutton's system: "He would have been less flattered, by being told
of the ingenuity and originality of his theory, than of the addition which it
had made to our knowledge of final causes" (1802, 122). But whereas final
cause and purpose are relentless themes on every page of Hutton's theoretical
discussion, Playfair hardly mentions the subject. I can find only two passages
that discuss final cause explicitly (121-122 and 129), while hundreds of
Playfair's pages recount the mechanics of Huttonian cycles in a world of
efficient causation.
But Playfair's most striking change is an alteration of sense, not emphasis. In
discussing field evidence, Playfair follows the primary tradition of geology
from its inception, and does not portray Hutton's primary idiosyncrasy—his
denial of history. 5 Playfair covers the same ground as Hutton, but his
discussions of unconformities (for example) express the traditional interest of
geologists in history for itself, whereas Hutton used historical events only to
establish his cycling world machine, never to record the slightest concern for
unique happenings in time.
Playfair discusses Hutton's unconformity (see Figure 3.1) as a sequence of
distinctive occurrences in time. He argues that the picture displays evidence
for three worlds in succession, and he discusses them from oldest to
youngest. He notes that the bottom strata contain sand and gravel from the
dissolution of a world still older—"the most ancient epocha, of which any
memorial exists in
5. This distinction seems to me vitally important, yet I believe that all commentators
have missed it. This difference has not been noted, I think, because Playfair's
descriptions in the historical mode seem so obvious and "natural" that they have not
been deemed odd or worthy of note as potentially distinct from Hutton—all because
Hutton's ahistorical perspective has not been properly documented.