Editing Uniformitarianism (section)

===20th century===
[[Stephen Jay Gould]]'s first scientific paper, "Is uniformitarianism necessary?" (1965), reduced these four assumptions to two.<ref>{{harvnb|Gould|1965}}</ref> He dismissed the first principle, which asserted spatial and temporal invariance of natural laws, as no longer an issue of debate. He rejected the third (uniformity of rate) as an unjustified limitation on scientific inquiry, as it constrains past geologic rates and conditions to those of the present. So, Lyell's uniformitarianism was deemed unnecessary.

Uniformitarianism was proposed in contrast to [[catastrophism]], which states that the distant past "consisted of epochs of paroxysmal and catastrophic action interposed between periods of comparative tranquility"<ref>William J. Whewell, ''Principles of Geology'', Charles Leyell, vol. II, London, 1832: Quart. Rev., v. 47, p. 103-123.</ref> Especially in the late 19th and early 20th centuries, most geologists took this interpretation to mean that catastrophic events are not important in geologic time; one example of this is the debate of the formation of the [[Channeled Scablands]] due to the catastrophic [[Missoula floods|Missoula]] glacial outburst floods. An important result of this debate and others was the re-clarification that, while the same principles operate in geologic time, catastrophic events that are infrequent on human time-scales can have important consequences in geologic history.<ref>Allen, E. A., et al., 1986, Cataclysms on the Columbia, Timber Press, Portland, OR. {{ISBN|978-0-88192-067-3}}

* "Bretz knew that the very idea of catastrophic flooding would threaten and anger ''the geological community''.  And here's why: among geologists in the 1920s, catastrophic explanations for geological events (other than volcanos or earthquakes) were considered wrong-minded to the point of heresy."  p. 42.
* "Consider, then, what Bretz was up against.  The very word 'Catastrophism' was heinous in the ears of geologists. ... It was a step backward, a betrayal of ''all that geological science had fought to gain''.  It was a heresy of the worst order."  p. 44
* "It was inevitable that sooner or later ''the geological community would rise up'' and attempt to defeat Bretz's 'outrageous hypothesis.'" p 49
* "Nearly 50 years had passed since Bretz first proposed the idea of catastrophic flooding, and now in 1971 ''his arguments had become a standard of geological thinking''." p. 71</ref>
Derek Ager has noted that "geologists do not deny uniformitarianism in its true sense, that is to say, of interpreting the past by means of the processes that are seen going on at the present day, so long as we remember that the periodic catastrophe is one of those processes.  Those periodic catastrophes make more showing in the stratigraphical record than we have hitherto assumed."<ref>{{cite book
  | last = Ager
  | first = Derek V.
  | title = The Nature of the Stratigraphical Record
  | edition = 3rd
  | publisher = John Wiley & Sons
  | date = 1993
  | location = Chichester, New York, Brisbane, Toronto, Singapore
  | pages = 83–84
  | isbn = 0-471-93808-4}}</ref>

Modern geologists do not apply uniformitarianism in the same way as Lyell. They question if rates of processes were uniform through time and only those values measured during the [[history of geology]] are to be accepted.<ref>{{cite book
  | last = Smith
  | first = Gary A
  |author2=Aurora Pun
   | title = How Does Earth Work: Physical Geology and the Process of Science (textbook)
  | publisher = Pearson/Prentice Hall
  | date = 2006
  | location = New Jersey
  | pages = 12
  | isbn = 0-13-034129-0}}</ref> The present may not be a long enough key to penetrating the deep lock of the past.<ref>{{cite book
  | last = Ager
  | first = Derek V.
  | title = The Nature of the Stratigraphical Record
  | edition = 3rd
  | publisher = John Wiley & Sons
  | date = 1993
  | location = Chichester, New York, Brisbane, Toronto, Singapore
  | pages = 81
  | isbn = 0-471-93808-4}}</ref>  Geologic processes may have been active at different rates in the past that humans have not observed.  "By force of popularity, uniformity of rate has persisted to our present day.  For more than a century, Lyell's rhetoric conflating axiom with hypotheses has descended in unmodified form.  Many geologists have been stifled by the belief that proper methodology includes an a priori commitment to gradual change, and by a preference for explaining large-scale phenomena as the concatenation of innumerable tiny changes."<ref name=Gould174>{{harvnb|Gould|1987|p=174}}</ref>

The current consensus is that [[History of Earth|Earth's history]] is a slow, gradual process punctuated by occasional natural catastrophic events that have affected Earth and its inhabitants.<ref>The Columbia Encyclopedia Sixth Edition, ''[http://www.bartleby.com/65/un/uniformi.html uniformitarianism] {{webarchive|url=https://web.archive.org/web/20060624122338/http://www.bartleby.com/65/un/uniformi.html |date=2006-06-24 }}'' © 2007 Columbia University Press.</ref> In practice it is reduced from Lyell's conflation, or blending, to simply the two philosophical assumptions. This is also known as the principle of geological actualism, which states that all past geological action was like all present geological action. The principle of [[actualism]] is the cornerstone of [[paleoecology]].<ref>{{cite book |last1=Forster |first1=Geoffrey P. |title=Half Life: Extending the Effective Lifespan of the Corporation |date=2010 |publisher=APAC Press |page=62 |url=https://books.google.com/books?id=jS7CAAAAQBAJ&pg=PA62 |language=en}}</ref>