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Uniformitarianism (science)
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Uniformitarianism, in the philosophy of science, assumes that the natural processes that operated in the past are the same as those that can be observed operating in the present. Its methodology is frequently summarized as "the present is the key to the past," because it holds that all things continue as they were from the beginning of the world.
The concept of uniformity in geological processes can be traced back to the Persian geologist, Avicenna (Ibn Sina), in The Book of Healing, published in 1027.
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Uniformitarianism, in the philosophy of science, assumes that the natural processes that operated in the past are the same as those that can be observed operating in the present. Its methodology is frequently summarized as "the present is the key to the past," because it holds that all things continue as they were from the beginning of the world.
The concept of uniformity in geological processes can be traced back to the Persian geologist, Avicenna (Ibn Sina), in The Book of Healing, published in 1027. Modern uniformitarianism was formulated by Scottish naturalists in the late 18th century, starting with the work of the geologist, James Hutton, which was refined by John Playfair and popularised by Charles Lyell's Principles of Geology in 1830. The term uniformitarianism was coined in 1832 by William Whewell, who also coined the term catastrophism for the idea that the Earth was shaped by a series of sudden, short-lived, violent events.
Forms of uniformitarianism
According to Reijer Hooykaas (1963), uniformitarianism is a family of four related propositions, not a single idea:
- Uniformity of law – the laws of nature are constant.
- 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 not changed over time.
- Uniformity of methodology – the appropriate hypotheses for explaining the geological past are those with analogy today.
None of these connotations requires another, and they are not all equally inferred by uniformitarians. Stephen Jay Gould's first scientific paper, Is uniformitarianism necessary? (1965), reduced these four interpretations to two, substantive and methodological uniformitarianism. He rejected the first as an unjustified limitation on scientific inquiry, as it constrains past geologic rates and conditions to those of the present. He dismissed the second principle, which asserted spatial and temporal invariance of natural laws, as no longer an issue of debate. Later, Gould expanded on these related propositions in Time's Arrow, Time's Cycle (1987), stating that Lyell conflated two different types of propositions: a pair of substantive hypotheses with a pair of Methodological assumptions.
Substantive:
- Uniformity of rate: Change is typically slow, steady, and gradual.
- Uniformity of state: Change is evenly distributed throughout space and time.
Methodologcal:
- Uniformity of law: Natural laws are constant across space and time.
- Uniformity of process: If a past phenomenon can be understood as the result of a process now acting in time and space, do not invent an extinct or unknown cause as its explanation.
The methodological assumptions are universally acclaimed by scientists, and embraced by all geologists. The substantive hypotheses were controversial and, in some cases, accepted by few. These divisions have been opposed by later geologists such as Celâl Sengör.
Uniformitarianism and Catastrophism
Uniformity of law is a basic principle of modern geology, which holds that the same fundamental geological processes operated in the past as do today. It was originally 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" Recently, uniformitarianism has accepted the possibility of catastrophic events in the past, leading to a combination of the two theories. For example, even Charles Lyell thought that ordinary geological processes would cause Niagara Falls to move upstream to Lake Erie within 10,000 years, leading to catastrophic flooding of a large part of North America. Thus the current scientific consensus is that Earth's history is a slow, gradual process punctuated by occasional natural catastrophic events that have affected Earth and its inhabitants.
Uniformitarianism is a generalization of the principle of actualism (geology), which states that all past geological action was like all present geological action. The principle of actualism is the cornerstone of paleoecology.
The concept of uniformitarianism in geology was first proposed in the 11th century by the Persian geologist, Avicenna (Ibn Sina, 980-1037), who provided the first uniformitarian explanations for geological processes in The Book of Healing. He observed that mountains were formed after a long sequence of events that predate human existence. While discussing the formation of mountains, he explained:
Later in the 11th century, the Chinese naturalist, Shen Kuo, also recognized the concept of 'deep time'.
After The Book of Healing was translated into Latin in the 12th century, a few other scientists also reasoned in uniformitarian terms, but the principle was not uniformly accepted until the late 18th century. The uniformitarian explanation of the formation of sedimentary rock in geological time was supported by the 18th-century father of geology, James Hutton and popularized by Charles Lyell. In the 18th and 19th centuries, the debate between the two theories was intense, as the interpretations of uniformitarianism clashed with the prevailing religious beliefs.
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