Uniformitarianism, in the philosophy of science, is the assumption that the natural processes operating in the past are the same as those that can be observed operating in the present. Its methodological significance is frequently summarized in the statement: "The present is the key to the past." Uniformitarianism is most closely associated with geology, but it is also used in astronomy, paleontology, and other sciences whose objects of study are in the past and (as a result) beyond the reach of direct observation. Uniformitarianism has its philosophical roots in antiquity, but it was refined and popularized by British scientists of the late 18th and early 19th centuries: notably James Hutton, John Playfair, Charles Lyell, and William Whewell (who coined the term). Philosophy of science studies the philosophical assumptions, foundations, and implications of science, including the formal sciences, natural sciences, and social sciences. ... World geologic provinces Oceanic crust  0-20 Ma  20-65 Ma  >65 Ma Geologic provinces  Shield  Platform  Orogen  Basin  Large igneous province  Extended crust Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason))[1] is the science and study of the solid matter of a celestial body, its composition... A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ... Paleontology or palaeontology (see Spelling differences) is the study of the history and development of life on Earth, including that of ancient plants and animals, based on the fossil record (evidence of their prehistoric existence as typically preserved in sedimentary rocks). ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... James Hutton, painted by Abner Lowe. ... Professor John Playfair FRSE (March 10, 1748 – July 20, 1819) was a Scottish scientist. ... Charles Lyell The frontispiece from Principles of Geology Sir Charles Lyell, 1st Baronet Kt (November 14, 1797 – February 22, 1875), Scottish lawyer, geologist, and populariser of uniformitarianism. ... William Whewell In later life William Whewell (May 24, 1794 – March 6, 1866) was an English polymath, scientist, Anglican priest, philosopher, theologian, and historian of science. ...

Four main forms of uniformitarianism

Uniformitarianism, though often treated as a single idea, is in fact a family of four related (but not identical) propositions. Paleontologist and evolutionary theorist Stephen Jay Gould usefully characterized them, in a 1965 paper ^[1] , as: Stephen Jay Gould Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... 1965 (MCMLXV) was a common year starting on Friday (the link is to a full 1965 calendar). ...

• 1) Uniformity of law;
• 2) Uniformity of kind;
• 3) Uniformity of degree; and
• 4) Uniformity of result.

The first sense of uniformitarianism was almost universally accepted and quickly became part of the scientific consensus; the fourth was almost universally rejected by Western scientists from the mid-19th century onward. The second and particularly the third senses remained controversial and (though more increasingly accepted in the 20th century) have been occasionally challenged by scientists who believe the presumption of uniformity (in the second and third senses) is unwarranted. Scientific consensus is the collective judgment, position, and opinion of scientists in a particular field of science at a particular time. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999...

Uniformitarianism and Catastrophism

Uniformitarianism is one of the most basic principles of modern geology, the observation that fundamentally the same geological processes that operate today also operated in the distant past. It exists in contrast with catastrophism, which states that Earth surface features originated suddenly in the past, by geological processes radically different to those currently occurring. Note, however, that many "catastrophic" events are perfectly compatible with uniformitarianism. For example, Charles Lyell thought that ordinary geological processes would cause Niagara Falls to move upstream to Lake Erie within 10000 years, leading to catastrophic flooding of a large part of North America. World geologic provinces Oceanic crust  0-20 Ma  20-65 Ma  >65 Ma Geologic provinces  Shield  Platform  Orogen  Basin  Large igneous province  Extended crust Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason))[1] is the science and study of the solid matter of a celestial body, its composition... Catastrophism is the theory that Earth has been affected by sudden, short-lived, violent events that were sometimes worldwide in scope. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... Charles Lyell The frontispiece from Principles of Geology Sir Charles Lyell, 1st Baronet Kt (November 14, 1797 – February 22, 1875), Scottish lawyer, geologist, and populariser of uniformitarianism. ...

Uniformitarianism is a generalisation of the principle of actualism, which states that present day-processes (astronomical, geological, paleontological,...) can be used to interpret past patterns. It is also known as "the present is the key to the past". The principle of actualism is the cornerstone of paleoecology. This article is about the philosophy actualism. ... Paleontology or palaeontology (see Spelling differences) is the study of the history and development of life on Earth, including that of ancient plants and animals, based on the fossil record (evidence of their prehistoric existence as typically preserved in sedimentary rocks). ... you doedd you flydndoedd ha ha ha ha aha ...

The geologist James Hutton was a pioneer of the principle, which was later popularised by Charles Lyell and influenced Charles Darwin. In the 18th and 19th centuries, the debate between the two theories was intense, since uniformitarianism seemed hard to reconcile with the prevailing religious beliefs of the time. Today, however, most if not all mainstream scientists support uniformitarianism as do most mainstream religious denominations. James Hutton, painted by Abner Lowe. ... Charles Lyell The frontispiece from Principles of Geology Sir Charles Lyell, 1st Baronet Kt (November 14, 1797 – February 22, 1875), Scottish lawyer, geologist, and populariser of uniformitarianism. ... Charles Robert Darwin FRS (12 February 1809 – 19 April 1882) was an English naturalist [1] who achieved lasting fame by producing considerable evidence that species originated through evolutionary change, at the same time proposing the scientific theory that natural selection is the mechanism by which such change occurs. ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... Various Religious symbols, including (first row) Christian, Jewish, Hindu, Bahai, (second row) Islam, tribal, Taoist, Shinto (third row) Buddhism, Sikh, Hindu, Jain (fourth row) Ayyavazhi, Diane de Poitiers, Maltese cross Religion is the adherence to codified beliefs and rituals that (generally) involve a faith in a spiritual nature and...

The understanding of slow geological processes have changed in several ways. Before continental drift (see plate tectonics) was recognized in the 20th century, the surface of Earth was believed to have remained generally unchanged since its formation. Cooling from a molten state was believed to have caused shrinkage, which caused mountains and folding of the surface. Currently it is accepted that much of the mantle is plastic and fluid, and the crust is slowly moving over it. It is this relative motion that produces folding, compression, rises, depressions, etc. Continental drift, first proposed as a theory by Alfred Wegener in 1912, is the movement of the Earths continents relative to each other. ... Bridge across the Álfagjá rift valley in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ...

In recent decades, the theory of uniformitarianism has been modified to reflect the discovery that catastrophic events occur today and have occurred in the Earth's past. The present is still the key to the past, meteorite impacts, giant earthquakes, tsunamis, and supervolcanic eruptions occur today as they have in the past and these events provide punctuations in an over-all gradual process. Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... This article is about the natural seismic phenomenon. ... For other meanings of tsunami, see tsunami (disambiguation). ... A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. ...

See also

• Gradualism
• Catastrophism
• Scientific consensus
• Paradigm shift
• History of geology
• History of paleontology
• History of the modern theory

Gradualism, in biology, holds that evolution occurs through the accumulation of slight modifications over a period of generations. ... Catastrophism is the theory that Earth has been affected by sudden, short-lived, violent events that were sometimes worldwide in scope. ... Scientific consensus is the collective judgment, position, and opinion of scientists in a particular field of science at a particular time. ... Paradigm shift is the term first used by Thomas Kuhn in his 1962 book The Structure of Scientific Revolutions to describe the process and result of a change in basic assumptions within the ruling theory of science. ... Wikipedia does not yet have an article with this exact name. ... The history of paleontology has been an ongoing effort to understand the history of life on Earth by understanding the fossil record left behind by living organisms. ...

Notes

External links

• Uniformitarianism discussed in great detail at PhysicalGeography.net
• Uniformitarianism discussed at the Geography section of About.com
• Uniformitarianism discussed at the Columbia Encyclopedia, sixth edition, on-line.