Editing Uniformitarianism (section)

====Lyell====
Lyell's uniformitarianism is a family of four related propositions, not a single idea:{{sfn|Hooykaas|1963}}
* Uniformity of law – the laws of nature are constant across time and space.
* Uniformity of methodology – the appropriate hypotheses for explaining the geological past are those with analogy today.
* Uniformity of kind – past and present causes are all of the same kind, have the same energy, and produce the same effects.
* Uniformity of degree – geological circumstances have remained the same over time.

None of these connotations requires another, and they are not all equally inferred by uniformitarians.<ref>David Cahan, 2003, ''From Natural Philosophy to the Sciences'', p 95 {{ISBN|978-0-226-08928-7}}.</ref>

[[Stephen Jay Gould|Gould]] explained Lyell's propositions in ''[[Time's Arrow, Time's Cycle]]'' (1987), stating that Lyell conflated two different types of propositions: a pair of '''''methodological assumptions''''' with a pair of '''''substantive hypotheses'''''. The four together make up Lyell's uniformitarianism.<ref name=Gould118>{{harvnb|Gould|1987|p=[https://archive.org/details/timesarrowtimesc00step_0/page/118 118]}}</ref>

=====Methodological assumptions=====
The two methodological assumptions below are accepted to be true by the majority of scientists and geologists. Gould claims that these philosophical propositions must be assumed before you can proceed as a scientist doing science.  "You cannot go to a rocky outcrop and observe either the constancy of nature's laws or the working of unknown processes.  It works the other way around." You first assume these propositions and "then you go to the outcrop."<ref name=Gould120>{{harvnb|Gould|1987|p=[https://archive.org/details/timesarrowtimesc00step_0/page/120 120]}}. "You first assume."</ref>

:* '''Uniformity of law across time and space''':  Natural laws are constant across space and time.<ref name=gould1987 />
::The axiom of uniformity of law <ref name="gould1965"/><ref name="simpson1963"/><ref name=gould1987>{{harvnb|Gould|1987|p=119}}, "''Making inferences about the past is wrapped up in the difference between studying the observable and the unobservable.'' In the observable, erroneous beliefs can be proven wrong and be inductively corrected by other observations. This is Popper's principle of [[falsifiability]]. However, ''past processes are not observable by their very nature.'' Therefore, '''the invariance of nature's laws must be assumed to come to conclusions about the past.''"</ref> is necessary in order for scientists to extrapolate (by inductive inference) into the unobservable past.<ref name=gould1965 /><ref name=gould1987 />  The constancy of natural laws must be assumed in the study of the past; else we cannot meaningfully study it.<ref name=gould1965 /><ref name=simpson1963 /><ref name=gould1987 /><ref>{{cite book| last=Hutton| first=J.| title=Theory of the Earth with Proofs and Illustrations| date=1795| page=297| quote=If the stone, for example, which fell today, were to rise again tomorrow, there would be an end of natural philosophy [i.e., science], ''our principles would fail, and we would no longer investigate the rules of nature from our observations''.}}</ref>

:* '''Uniformity of process across time and space''':  Natural processes are constant across time and space.

::Though similar to uniformity of law, this second ''a priori'' assumption, shared by the vast majority of scientists, deals with geological causes, not physicochemical laws.<ref>{{harvnb|Gould|1984|p=11}},  "As such, it is another ''a priori'' methodological assumption shared by most scientists and not a statement about the empirical world."</ref>  The past is to be explained by processes acting currently in time and space rather than inventing extra esoteric or unknown processes ''without good reason'',<ref>{{harvnb|Gould|1987|p=120}}, "We should try to explain the past by causes now in operation without inventing extra, fancy, or unknown causes, however plausible in logic, if available processes suffice."</ref><ref>{{harvnb|Hooykaas|1963|p=38}}, "Strict uniformitarianism may often be a guarantee against pseudo-scientific phantasies and loose conjectures, but it makes one easily forget that the principle of uniformity is not a law, not a rule established after comparison of facts, but a methodological principle, preceding the observation of facts ... It is the logical principle of parsimony of causes and of the economy of scientific notions. By explaining past changes by analogy with present phenomena, a limit is set to conjecture, for there is only one way in which two things are equal, but there is an infinity of ways in which they could be supposed different."</ref> otherwise known as parsimony or [[Occam's razor]].

=====Substantive hypotheses=====
The substantive hypotheses were controversial and, in some cases, accepted by few.<ref name=Gould118 />  These hypotheses are judged true or false on empirical grounds through scientific observation and repeated experimental data. This is in contrast with the previous two philosophical assumptions<ref name="Gould120" /> that come before one can do science and so cannot be tested or falsified by science.

:* '''Uniformity of rate across time and space''':  Change is typically slow, steady, and gradual.<ref name="Gould120" />

::Uniformity of rate (or [[gradualism]]) is what most people (including geologists) think of when they hear the word "uniformitarianism", confusing this hypothesis with the entire definition.  As late as 1990, Lemon, in his textbook of stratigraphy, affirmed that "The uniformitarian view of earth history held that all geologic processes proceed continuously and at a very slow pace."<ref>Lemon, R. R. 1990. ''Principles of stratigraphy''. Columbus, Ohio: Merrill Publishing Company. p. 30</ref>

::Gould explained Hutton's view of uniformity of rate; mountain ranges or grand canyons are built by the accumulation of nearly insensible changes added up through vast time.  Some major events such as floods, earthquakes, and eruptions, do occur.  But these catastrophes are strictly local.  They neither occurred in the past nor shall happen in the future, at any greater frequency or extent than they display at present. In particular, the whole earth is never convulsed at once.<ref name=Gould120s>{{harvnb|Gould|1987|pp=120–121}}</ref>

:* '''Uniformity of state across time and space''':  Change is evenly distributed throughout space and time.<ref name=Gould123>{{harvnb|Gould|1987|p=[https://archive.org/details/timesarrowtimesc00step_0/page/123 123]}}</ref>

::The uniformity of state hypothesis implies that throughout the history of our earth there is no progress in any inexorable direction. The planet has almost always looked and behaved as it does now.  Change is continuous but leads nowhere. The earth is in balance: a dynamic [[steady state]].<ref name=Gould123 />