Uniformitarianism

views updated May 21 2018

Uniformitarianism

Resources

Uniformitarianism is commonly oversimplified where stated in geological textbooks as the present is a guide to interpreting the past (or words to that effect). This explanation, however, is not correct about the true meaning of uniformitarianism. In order to understand uniformitarianism, one must examine its roots in the Enlightenment era (c. 17501850) and how the term has been distorted in meaning since that time.

Geology is an historical science, yet the phenomena and processes studied by geologists operated under non-historical natural systems that are independent of the time in which they operated. It is clear from the insights of one of geologys founding fathers of the Enlightenment era, James Hutton (17261797), that he understood this fact very well. In Theory of the Earth (1795), he stated: In examining things present, we have data from which to reason with regard to what has been; and, from what has actually been, we have data for concluding with regard to that which is to happen thereafter. With his book, Hutton popularized the notion of examining things presentwith regard to what has been, but gave the concept no specific name. Hutton did not use the term uniformitarianism and used the word uniformity only rarely.

Charles Lyell (17971875), one of geologys founding fathers from later in the Enlightenment era, wrote about the subject matter of uniformitarianism (but did not use that specific term) in his widely read text, Principles of Geology (1830). Partly in response to stri-dent criticism that his notions about geology did not conform to Biblical edicts about supernatural catastrophic events, Lyell developed a much more radical and extreme view of the subject matter of the uniformity of nature. Careful reading of what Lyell laid out in his discussion of the uniformity of nature shows that he embraced both the concept of Hutton, which can be summarized as a uniformity of known causes or processes throughout time, and his own separate view that there must be a uniformity of process rates. The latter, more radical aspect of Lyells uniformity of nature was intended to be a statement of general principle to counter the catastrophist interpretations of the past set forth by geologists of the day who were more inclined to look to the scriptures for their geological interpretations. In Lyells view, a strong notion of uniformity of rates precluded divine (i.e., catastrophic) intervention.

In 1837, the name uniformitarianism was coined by William Whewell (17941866) as a term meant to convey Huttons sense of order and regularity in the operation of nature and Lyells sense that there was a uniformity of rates of geological processes through time. It is Whewells definition that became the most common definition of uniformitarianism.

Lyells work was influential, and he succeeded in imbuing generations of geologists with the notion of a dual foundation for uniformity of nature. This dual foundation encompassed both uniformity of causes and uniformity of intensity. The former view is more commonly called actualism, and the latter, gradualism. In large part, the presence of Lyells strongly defended gradualism succeeded in freeing nineteenth century geology from the firm grasp of Biblical preconception and allowed it to develop as a legitimate science.

One of the most elegant statements about actualism was made by John Playfair in his book, Illustrations of the Huttonian Theory (1802). He said: Amid all the revolutions of the globe the economy of Nature has been uniform, and her laws are the only things that have resisted the general movement. The rivers and the rocks, the seas, and the continents have been changed in all their parts; but the laws which describe those changes, and the rules to which they are subject, have remained invariably the same. Actualism is not unique to geology, as it is really a basic and broad scientific concept of many fields. Even though Playfair mentions laws, it is, of course, nature itself that is constant, not laws that have been written by people in order to try to predict nature.

The other side of Lyells uniformity of nature, i.e., gradualism, has no such elegant prose behind it. It has been referred to in inglorious terms by some of the leading minds of our time as false and stifling to hypothesis formation, a blatant lie, and a superfluous term best confined to the past history of geology. In other words, gradualism is no longer considered a valid idea.

Because uniformitarianism has this historical component of uniformity of process rates (i.e., gradualism), many writers have advocated its elimination from the geological vocabulary. Others argue that should be retained, but with careful notation about its historical meaning. Some writers ignore this historical debate and continue to tout the term uniformitarianism as the most basic principle of geology. The range of misguided meanings of this term from some recent geology texts includes definitions that span the gamut from something near the nineteenth century meaning to the assumption that the Earth is very old, to the logical method of geologic investigation.

Careful analysis of geological texts and recent scientific articles shows that there are at least 12 basic fallacies about uniformitarianism, (such as those explained by University of Wisconsin Geology Professor James H. Shea), which are perpetuated by some writers. These are:

  1. Uniformitarianism is unique to geology.
  2. Uniformitarianism was first discussed by James Hutton.
  3. Uniformitarianism was named by Lyell, who gave us its modern meaning.
  4. Uniformitarianism is the same as actualism, and should be re-named actualism.
  5. Uniformitarianism holds that only processes that are currently active could have occurred in the geologic past.
  6. Uniformitarianism holds that rates and intensities of geologic processes are constant through time.
  7. Uniformitarianism holds that only non-catastrophic, or gradual processes have operated during geologic time.
  8. Uniformitarianism holds that Earths conditions have changed little over geologic time.
  9. Uniformitarianism holds that Earth is very old.
  10. Uniformitarianism is a testable hypothesis, theory, or law.
  11. Uniformitarianism applies to the past only as far back as present conditions have existed on Earths surface.
  12. Uniformitarianism holds only that the governing laws of nature are constant through space and geologic time.

Through historical analysis of uniformitarianism, one is able to see how these twelve common conceptions are false and misleading. Most scientists argue that uniformitarianism should be kept in its proper historical perspective in the future, and that a more specific term like actualism might supplant uniformitarianism in places where the word is meant to convey strictly the modern concept of uniformity of causes.

See also Stratigraphy (archaeology); Stratigraphy.

Resources

PERIODICALS

Gould, S.J. Is Uniformitarianism Necessary? American Journal of Science. 263 (1965): 22328.

Gould, S.J. Reply to C.R. Longwells Criticism of Is Uniformitarianism Necessary? American Journal of Science. 263 (1965): 91921.

Shea, J.H. Twelve Fallacies of Uniformitarianism. Geology. (September, 1982): 457.

David T. King, Jr.

Uniformitarianism

views updated May 29 2018

Uniformitarianism

Uniformitarianism is commonly oversimplified where stated in geological textbooks as "the present is a guide to interpreting the past" (or words to that effect). This explanation, however, is not correct about the true meaning of uniformitarianism. In order to understand uniformitarianism, one must examine its roots in the Enlightenment era (c. 1750–1850) and how the term has been distorted in meaning since that time.


Geology is an historical science, yet the phenomena and processes studied by geologists operated under nonhistorical natural systems that are independent of the time in which they operated. It is clear from the insights of one of geology's founding fathers of the Enlightenment era, James Hutton (1726–1797), that he understood this fact very well. In Theory of the Earth (1795), he stated: "In examining things present, we have data from which to reason with regard to what has been; and, from what has actually been, we have data for concluding with regard to that which is to happen thereafter." With his book, Hutton popularized the notion of "examining things present...with regard to what has been," but gave the concept no specific name. Hutton did not use the term uniformitarianism and used the word "uniformity" only rarely.

Charles Lyell (1797–1875), one of geology's founding fathers from later in the Enlightenment era, wrote about the subject matter of uniformitarianism (but did not use that specific term) in his widely read text, Principles of Geology (1830). Partly in response to strident criticism that his notions about geology did not conform to Biblical edicts about supernatural catastrophic events, Lyell developed a much more radical and extreme view of the subject matter of the "uniformity of nature." Careful reading of what Lyell laid out in his discussion of the "uniformity of nature" shows that he embraced both the concept of Hutton, which can be summarized as a uniformity of known causes or processes throughout time, and his own separate view that there must be a uniformity of process rates. The latter, more radical aspect of Lyell's "uniformity of nature" was intended to be a statement of general principle to counter the catastrophist interpretations of the past set forth by geologists of the day who were more inclined to look to the scriptures for their geological interpretations. In Lyell's view, a strong notion of uniformity of rates precluded divine (i.e., catastrophic) intervention.

In 1837, the name uniformitarianism was coined by William Whewell (1794–1866) as a term meant to convey Hutton's sense of order and regularity in the operation of nature and Lyell's sense that there was a uniformity of rates of geological processes through time. It is Whewell's definition that became the most common definition of uniformitarianism.

Lyell's work was influential, and he succeeded in imbuing generations of geologists with the notion of a dual foundation for "uniformity of nature." This dual foundation encompassed both uniformity of causes and uniformity of intensity. The former view is more commonly called actualism, and the latter, gradualism. In large part, the presence of Lyell's strongly defended gradualism succeeded in freeing nineteenth century geology from the firm grasp of Biblical preconception and allowed it to develop as a legitimate science.

One of the most elegant statements about actualism was made by John Playfair in his book, Illustrations of the Huttonian Theory (1802). He said: "Amid all the revolutions of the globe the economy of Nature has been uniform, and her laws are the only thing that have resisted the general movement. The rivers and the rocks , the seas, and the continents have been changed in all their parts; but the laws which describe those changes, and the rules to which they are subject, have remained invariably the same." Actualism is not unique to geology, as it is really a basic and broad scientific concept of many fields. Even though Playfair mentions laws, it is, of course, nature itself that is constant, not laws that have been written by people in order to try to predict nature.

The other side of Lyell's "uniformity of nature," i.e., gradualism, has no such elegant prose behind it. It has been referred to in inglorious terms by some of the leading minds of our time as "false and stifling to hypothesis formation," "a blatant lie," and "a superfluous term...best confined to the past history of geology." In other words, gradualism is no longer considered a valid idea.

Because uniformitarianism has this historical component of uniformity of process rates (i.e., gradualism), many writers have advocated its elimination from the geological vocabulary. Others argue that should be retained, but with careful notation about its historical meaning. Some writers ignore this historical debate and continue to tout the term uniformitarianism as the most basic principle of geology. The range of misguided meanings of this term from some recent geology texts includes definitions that span the gamut from something near the nineteenth century meaning to the assumption that the Earth is very old, to the logical method of geologic investigation.

Careful analysis of geological texts and recent scientific articles shows that there are at least 12 basic fallacies about uniformitarianism, (such as those explained by University of Wisconsin Geology Professor James H. Shea), which are perpetuated by some writers. These are:

  • Uniformitarianism is unique to geology.
  • Uniformitarianism was first discussed by James Hutton.
  • Uniformitarianism was named by Lyell, who gave us its modern meaning.
  • Uniformitarianism is the same as actualism, and should be re-named actualism.
  • Uniformitarianism holds that only processes that are currently active could have occurred in the geologic past.
  • Uniformitarianism holds that rates and intensities of geologic processes are constant through time.
  • Uniformitarianism holds that only non-catastrophic, or gradual processes have operated during geologic time.
  • Uniformitarianism holds that Earth's conditions have changed little over geologic time.
  • Uniformitarianism holds that Earth is very old.
  • Uniformitarianism is a testable hypothesis, theory, or law.
  • Uniformitarianism applies to the past only as far back as present conditions have existed on Earth's surface.
  • Uniformitarianism holds only that the governing laws of nature are constant through space and geologic time .

Through historical analysis of uniformitarianism, one is able to see how these twelve common conceptions are false and misleading. Most scientists argue that uniformitarianism should be kept in its proper historical perspective in the future, and that a more specific term like actualism might supplant uniformitarianism in places where the word is meant to convey strictly the modern concept of uniformity of causes.

See also Stratigraphy (archeology); Stratigraphy.


Resources

books

Hancock, P.L., and B.J. Skinner, eds. The Oxford Companion to the Earth. New York: Oxford University Press, 2000.

periodicals

Gould, S.J. "Is Uniformitarianism Necessary?" American Journal of Science 263 (1965): 223–28.

Gould, S.J. "Reply to C.R. Longwell's Criticism of 'Is Uniformitarianism Necessary?'" American Journal of Science 263 (1965): 919–21.

Shea, J.H. "Twelve Fallacies of Uniformitarianism." Geology (September 1982): 457.


David T. King, Jr.

Uniformitarianism

views updated May 29 2018

Uniformitarianism

The concept of uniformitarianism is commonly oversimplified in geological textbooks as "the present is a guide to interpreting the past" (or words to that effect). This explanation, however, is not correct about the true meaning of uniformitarianism. In order to understand uniformitarianism, one must examine its roots in the Enlightenment era (c. 17501850) and how the term has been distorted in meaning since that time.

Geology is a historical science, yet the phenomena and processes studied by geologists operated under non-historical natural systems that are independent of the time in which they operated. It is clear from the insights of one of geology's founding fathers of the Enlightenment era, James Hutton (17261797), that he understood this fact very well. In Theory of the Earth (1795), he stated: "In examining things present, we have data from which to reason with regard to what has been; and, from what has actually been, we have data for concluding with regard to that which is to happen thereafter." With his book, Hutton popularized the notion of "examining things present...with regard to what has been," but gave the concept no specific name. Hutton did not use the term uniformitarianism and used the word 'uniformity' only rarely.

Charles Lyell (17971875), one of geology's founding fathers from later in the Enlightenment era, wrote about the subject matter of uniformitarianism (but did not use that specific term) in his widely read text, Principles of Geology (1830). Partly in response to strident criticism that his notions about geology did not conform to Biblical edicts about supernatural catastrophic events, Lyell developed a much more radical and extreme view of the subject matter of the "uniformity of nature." Careful reading of what Lyell laid out in his discussion of the "uniformity of nature" shows that he embraced both the concept of Hutton, which can be summarized as a uniformity of known causes or processes throughout time, and his own separate view that there must be a uniformity of process rates. The latter, more radical aspect of Lyell's "uniformity of nature" was intended to be a statement of general principle to counter the catastrophist interpretations of the past set forth by geologists of the day who were more inclined to look to the scriptures for their geological interpretations. In Lyell's view, a strong notion of uniformity of rates precluded divine (i.e., catastrophic) intervention.

In 1837, the name uniformitarianism was coined by William Whewell (17941866) as a term meant to convey Hutton's sense of order and regularity in the operation of nature and Lyell's sense that there was a uniformity of rates of geological processes through time. It is Whewell's definition that became the most common definition of uniformitarianism.

Lyell's work was influential, and he succeeded in imbuing generations of geologists with the notion of a dual foundation for "uniformity of nature." This dual foundation encompassed both uniformity of causes and uniformity of intensity. The former view is more commonly called actualism today, and the latter, gradualism. In large part, the presence of Lyell's strongly defended gradualism succeeded in freeing nineteenth century geology from the firm grasp of Biblical preconception and allowed it to develop as a free, legitimate science.

One of the most elegant statements about (what is now called) actualism was made by John Playfair in his book, Illustrations of the Huttonian Theory (1802). He said: "Amid all the revolutions of the globe the economy of Nature has been uniform, and her laws are the only thing that have resisted the general movement. The rivers and the rocks, the seas , and the continents have been changed in all their parts; but the laws which describe those changes, and the rules to which they are subject, have remained invariably the same." Actualism is not unique to geology, as it is really a basic and broad scientific concept of many fields. Even though Playfair mentions laws, it is, of course, nature herself that is constant, not laws, which have been written by people in order to try to predict nature.

The other side of Lyell's "uniformity of nature," i.e., gradualism, has no such elegant prose behind it. It has been referred to in inglorious terms by some of the leading minds of our time as "false and stifling to hypothesis formation," "a blatant lie," and "a superfluous term...best confined to the past history of geology." In other words, gradualism is no longer considered a valid idea.

Because uniformitarianism has this historical component of uniformity of process rates (i.e., gradualism), many writers have advocated its elimination from the geological vocabulary. Others argue that it should be retained, but with careful notation about its historical meaning. Some writers ignore this historical debate and continue to tout the term uniformitarianism as the most basic principle of geology. The range of misguided meanings of this term from some recent geology texts includes definitions that span the gamut from something near the nineteenth century meaning to the assumption that Earth is very old, to the logical method of geologic investigation.

Careful analysis of geological texts and recent scientific articles shows that there are at least 12 basic fallacies about uniformitarianism, which are perpetuated by some writers. These are:

  1. Uniformitarianism is unique to geology;
  2. Uniformitarianism was first discussed by James Hutton;
  3. Uniformitarianism was named by Lyell, who gave us its modern meaning;
  4. Uniformitarianism is the same as actualism, and should be renamed actualism;
  5. Uniformitarianism holds that only processes that are currently active could have occurred in the geologic past;
  6. Uniformitarianism holds that rates and intensities of geologic processes are constant through time;
  7. Uniformitarianism holds that only non-catastrophic or gradual processes have operated during geologic time;
  8. Uniformitarianism holds that Earth's conditions have changed little over geologic time;
  9. Uniformitarianism holds that the earth is very old;
  10. Uniformitarianism is a testable hypothesis, theory, or law;
  11. Uniformitarianism applies to the past only as far back as present conditions have existed on the earth's surface;
  12. Uniformitarianism holds only that the governing laws of nature are constant through space and geologic time.

In the historical analysis of uniformitarianism above, we have seen how these 12 common conceptions are false and misleading. Most scientists argue that uniformitarianism should be kept in its proper historical perspective in the future, and that a more specific term like actualism might supplant uniformitarianism in places where the word is meant to convey strictly the modern concept of uniformity of causes.

See also Geologic time; Stratigraphy

Uniformitarianism

views updated Jun 27 2018

Uniformitarianism

Introduction

Uniformitarianism is the general concept that the history of Earth, both in the rock and fossil record, is one of gradual change and uniform conditions. Uniformitarianism was born in the nineteenth century as a philosophical reaction to Biblical catastrophism, a point of view emphasizing sudden, violent events in Earth's history— typically of Biblical origin. Uniformitarianism was taken quite literally, and has had a long history in geology.

However, in the modern holistic view of geological science, there is good evidence for many sudden, violent events as well as gradual change. Many people confuse uniformitarianism with actualism, the modern concept that study of current processes and their products allows us to understand past processes and products. Uniformitarianism is as outmoded as the ancient concept of catastrophism, however.

Historical Background and Scientific Foundations

Uniformitarianism is deeply rooted in nineteenth-century geology, which had a scientific and philosophic struggle with Biblical catastrophism in its early days. With the advent of the geological view of deep time (or vast geological history), uniformitarianism developed as an opposing viewpoint to Biblical catastrophism. In the uniformitarian view, Earth history is entirely gradual and changes are uniform with time. In particular, the rate of change with time is uniform.

The view of uniformitarianism was taken quite literally for many decades. For this reason, sudden, violent origins for geological features and rock formations were considered untenable or were relegated to secondary status as a hypothesis. Today, a more holistic approach to geological interpretation prevails and features and formations are interpreted as the facts warrant.

Legacies of Uniformitarianism

One of the legacies of uniformitarianism is neglect of hypotheses dealing with sudden, violent processes in interpretation of events such as mass extinction of organisms, rapid climate change, and extraterrestrial bombardment by asteroids and comets. Uniformitarianism also had a profound effect upon interpretation of evolutionary processes, thus making it quite difficult for new ideas about rapid development of new species to be accepted.

Uniformitarianism as a philosophy was important in largely extinguishing Biblical catastrophism from geological interpretation. Thus, it helped geology become a mainstream science during the nineteenth century emergence of the earth sciences.

Uniformitarianism and What Is Not Uniformitarianism

In a discussion of uniformitarianism, it is also useful to note what uniformitarianism is not, because so many writers ascribe different meanings to this term. Some writers say that uniformitarianism and actualism are the same, but they are not. Others state that uniformitarianism holds that only processes and products we see today could have existed in the past, and this is also not true. It is said in some places that uniformitarianism somehow holds that geological conditions have not changed over time. Or, it is sometimes said that uniformitarianism is in some way a testable hypothesis. Some authors even say that uniformitarianism requires that the laws of nature are stable over time. All these things are misinterpretations of uniformitarianism that the nineteenth-century geologists who first used this term and concept never envisioned.

Uniformitarianism, as a concept and term, is commonly attributed to the founding fathers of geology. However, this is not correct. James Hutton (1726–1797), who was the early Enlightenment Era father of geology, wrote about the concept of actualism (but did not use that word) and about the order and regularity of the operation of nature. Charles Lyell (1797–1875), who was a founding father of geology from later in the Enlightenment, wrote about uniformity of rates of processes in nature. Like Hutton, he did not use the term uniformitarianism. It was much lesser-known eighteenth-century geologist William Whewell (1794–1866) who coined the term uniformitarianism, as an amalgam of the Hutton concept of order and regularity and the Lyell concept of uniformity of rates.

WORDS TO KNOW

ACTUALISM: The doctrine that past events in Earth's geological and biological history were the outcome of processes like those that we see in operation today. Actualism asserts uniformity of process throughout geological history, and is one of the elements of uniformitarianism.

CATASTROPHISM: School of thought in geology which holds that the rates of processes shaping Earth have varied greatly in the past, occasionally acting with violent suddenness (catastrophes).

INDUSTRIAL REVOLUTION: The period, beginning about the middle of the eighteenth century, during which humans began to use steam engines as a major source of power.

Impacts and Issues

In the traditional (nineteenth century) view of uniformitarianism, all modern and past changes of conditions on Earth were gradual. It is not clear how the modern acceleration in climate change (and the quantifiable human effects in helping speed this change) would have been viewed, if they were known at the time. Uniformitarianism was first written about in England at about the same time as the Industrial Revolution took hold in that country. Thus, human-induced acceleration in global warming was not an issue then and weather records of the day would not have revealed much evidence of long-term change (weather records were scanty then as well). Climate change as we know it today, therefore, did not play a dominant role in development of the concept of uniformitarianism.

See Also Abrupt Climate Change; Catastrophism.

BIBLIOGRAPHY

Books

Berggren, W. A., and J. A. Van Couvering, eds. Catastrophes and Earth History: The New Uniformitarianism. Princeton, NJ: Princeton University Press, 1984.

Periodicals

Shea, J. H. “Twelve Fallacies of Uniformitarianism.” Geology 10 (1982): 455–460.

Web Sites

Pidwirny, Michael. “Introduction to the Lithosphere: Concept of Uniformitarianism.” PhysicalGeography.net, 2007. <http://www.physicalgeography.net/fundamentals/10c.html> (accessed December 3, 2007).

David T. King Jr.

Uniformitarianism

views updated May 18 2018

Uniformitarianism

In geology, uniformitarianism is the belief that Earth's physical structure is the result of currently existing forces that have operated uniformly (in the same way) since Earth formed roughly 4.5 billion years ago. Mountains rise, valleys deepen, and sand grains collect now the same way they uplifted, eroded, and deposited over these millions of years. The activities of the present are a key to those of the past.

Early theories of Earth's formation were based on a literal reading of the Biblical book of Genesis. In the mid-sixteenth century, Irish Catholic bishop James Ussher (15811656) counted the ages of Biblical characters and calculated Earth to be only 6,000 years old. Bound by tradition (and even by law) to work within this short time frame, scientists of the time had to explain the placement and composition of rocks with more acceptable theories like catastrophismthe belief that Earth changes suddenly during cataclysmic earthquakes, floods, or eruptions.

In 1785, Scottish geologist James Hutton (17261797) electrified the geologic community when he presented a theory on the formation of Earth that contradicted the Bible-based one. The major elements contained in his Theory of the Earth were later termed "uniformitarianism." Hutton maintained that:

1. The fossilized strata (horizontal layers of material) of Earth, originating from the bottom of the sea, were formed by natural processes driven by heat energy from Earth's core.

2. The present continents' shapes indicated that they had once belonged to a singular landmass. Hutton added that the current disintegration and erosion of surface rock would lead to the formation of future continents.

3. These processes that shaped Earth were natural and operated very slowly, and most of this activity predated humankind by much more than a few days.

Eventually, the scientific community embraced uniformitarianism because it explained a majority of geological mysteries and did not rely on any kind of divine intervention to bring about change.

Modern uniformitarianism differs slightly from its original version. It agrees that the laws of nature operate the same way today as they did millions of years ago, with one exception: the processes that shape Earth operate the same as they always have, but the speed and intensity of those processes may vary. Volcanoes erupt as they have all along (as shown in rocks), but there were times of greater volcanic activity than today. Land erodes now as it did millions of year ago, but land eroded faster when there were no plants to stop rocks and soil from washing into the seas.

Uniformitarianism allows us to interpret the events of the past in rocks; it allows us to write the history of Earth. In addition to allowing the interpretation of the past, uniformitarianism allows for the prediction of the future. Understanding how and when rivers flood, what causes earthquakes and where they are likely to occur, or how and when a volcano will erupt can limit damage from these events. Although short-term prediction still eludes geologists, long-range forecasting of such disasters can ultimately saves lives and property.

[See also Catastrophism ]

uniformitarianism

views updated May 23 2018

uniformitarianism The principle proposed by James Hutton (1726–97) and paraphrased as ‘the present is the key to the past’, that the surface of the Earth has been formed and shaped by processes similar to those which can be observed today. This is a considerable oversimplification, since processes that occurred in historical times may not be occurring now, or may not be observable now, and vice versa. See also actualism.

uniformitarianism

views updated May 08 2018

uniformitarianism (actualism) The principle proposed by James Hutton and paraphrased succinctly as ‘the present is the key to the past’. This is a considerable oversimplification, since processes that occurred in historical times may not be occurring now, or may not be observable now, and vice versa.

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