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reviewed the second edition of Lyell's topic, lumped the two meanings together
under the unwieldy name “uniformitarianism,” which stuck. Whewell posed the
essentialquestionofgeology:“Havethechangeswhichleadusfromonegeologic-
al state to another been, on a long average, uniform in their intensity, or have they
consisted of epochs of paroxysmal and catastrophic action, interposed between
periods of comparative tranquillity?” He sagely predicted that the question “will
probably for some time divide the geological world into two sects, which may per-
haps be designated as the Uniformitarians and the Catastrophists.”
17
The defense would go on to point out that the constancy of law and process,
which Gould has called
methodological uniformitarianism
, describes not how the
Earth works but how geologists ought to work. They reject supernatural explana-
tions and employ commonplace, simple processes before appealing to rare, com-
plicated ones. Of course, this is not the only way that science works; it is nothing
more than common sense. William of Ockham expressed it well in the fourteenth
century: “One should not assume the existence of more things than are logically
necessary.” All scientists reason from effects back to causes. Nothing is special
about methodological uniformity; it says merely that geology is a science.
Lyellbelievedsostronglyintheuniformityofrateandstate,whichGouldcalled
substantive uniformitarianism
, that he wrote,
But should we ever establish by unequivocal proofs, that certain agents have, at particular peri-
ods of past time, been more potent instruments of change over the entire surface of the Earth
than they now are, it will be more consistent with philosophical caution to presume, that after
an interval of quiescence they will recover their pristine vigor, than to regard them as worn
out.
18
But by the late nineteenth century, geologists had already found unequivocal
evidence that substantive uniformity is false: earth history is marked by change.
Glaciers have advanced over the continents and retreated; seas have drowned the
continents and withdrawn; mountain ranges have risen and worn away; parts of the
Earth now cold were once warm and
vice versa
.
The coup de grace to an unchanging Earth was the progression shown by the
fossil record, leading from the simplest life forms in Precambrian rocks to mod-
ern
Homo sapiens
. Lyell accepted evolution only in the 1866 edition of his
Prin-
ciples
and then, Gould believes, only because “it permitted him to preserve all oth-
er meanings of uniformity.”
19
One type of uniformitarianism amounts to the statement that geology is a scien-
ce; the second, which requires the adoption and maintenance of an a priori position
regardless of the evidence, amounts to the statement that geology is not a science.
