Life Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! == History of study == === Materialism === {{main|Materialism}} Some of the earliest theories of life were materialist, holding that all that exists is matter, and that life is merely a complex form or arrangement of matter. [[Empedocles]] (430 BC) argued that everything in the universe is made up of a combination of [[Classical element|four eternal "elements"]] or "roots of all": earth, water, air, and fire. All change is explained by the arrangement and rearrangement of these four elements. The various forms of life are caused by an appropriate mixture of elements.<ref>{{cite web |first1=Richard |last1=Parry |date=4 March 2005 |title=Empedocles |website=Stanford Encyclopedia of Philosophy |url=http://plato.stanford.edu/entries/empedocles/ |access-date=25 May 2012 |archive-date=13 May 2012 |archive-url=https://web.archive.org/web/20120513201301/http://plato.stanford.edu/entries/empedocles/ |url-status=live }}</ref> [[Democritus]] (460 BC) was an [[Atomism|atomist]]; he thought that the essential characteristic of life was having a [[soul]] (''psyche''), and that the soul, like everything else, was composed of fiery atoms. He elaborated on fire because of the apparent connection between life and heat, and because fire moves.<ref name=democritus>{{cite web |first1=Richard |last1=Parry |date=25 August 2010 |title=Democritus |website=Stanford Encyclopedia of Philosophy |url=http://plato.stanford.edu/entries/democritus/#4 |access-date=25 May 2012 |archive-date=30 August 2006 |archive-url=https://web.archive.org/web/20060830030642/http://plato.stanford.edu/entries/democritus/#4 |url-status=live }}</ref> [[Plato]], in contrast, held that the world was organized by permanent [[Theory of Forms|forms]], reflected imperfectly in matter; forms provided direction or intelligence, explaining the regularities observed in the world.<ref>{{cite book |title=Cause and Explanation in Ancient Greek Thought |last=Hankinson |first=R.J. |publisher=Oxford University Press |date=1997 |isbn=978-0-19-924656-4 |url=https://books.google.com/books?id=iwfy-n5IWL8C |page=125 |df=dmy-all |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194747/https://books.google.com/books?id=iwfy-n5IWL8C |url-status=live }}</ref> The [[mechanism (philosophy)|mechanistic]] materialism that originated in [[ancient Greece]] was revived and revised by the French philosopher [[René Descartes]] (1596–1650), who held that animals and humans were assemblages of parts that together functioned as a machine. This idea was developed further by [[Julien Offray de La Mettrie]] (1709–1750) in his book ''L'Homme Machine''.<ref>{{cite book |last=de la Mettrie |first=J.J.O. |date=1748 |title=L'Homme Machine |trans-title=Man a machine |publisher=Elie Luzac |place=Leyden }}</ref> In the 19th century the advances in [[cell theory]] in biological science encouraged this view. The [[evolution]]ary theory of [[Charles Darwin]] (1859) is a mechanistic explanation for the origin of species by means of [[natural selection]].<ref>{{cite book |first1=Paul |last1=Thagard |title=The Cognitive Science of Science: Explanation, Discovery, and Conceptual Change |publisher=MIT Press |date=2012 |isbn=978-0-262-01728-2 |pages=204–205 |url=https://books.google.com/books?id=HrJIV19_nZYC&pg=PA204 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194751/https://books.google.com/books?id=HrJIV19_nZYC&pg=PA204 |url-status=live }}</ref> At the beginning of the 20th century [[Stéphane Leduc]] (1853–1939) promoted the idea that biological processes could be understood in terms of physics and chemistry, and that their growth resembled that of inorganic crystals immersed in solutions of sodium silicate. His ideas, set out in his book ''La biologie synthétique''<ref>{{cite book |last=Leduc |first=Stéphane |author-link=Stéphane Leduc |date=1912 |title=La Biologie Synthétique |trans-title =Synthetic Biology |publisher=Poinat |place =Paris}}</ref> was widely dismissed during his lifetime, but has incurred a resurgence of interest in the work of Russell, Barge and colleagues.<ref>{{cite journal |doi=10.1089/ast.2013.1110 |title=The Drive to Life on Wet and Icy Worlds|year=2014|last1=Russell |first1=Michael J. |last2=Barge |first2=Laura M. |last3=Bhartia |first3=Rohit |last4=Bocanegra |first4=Dylan |last5=Bracher |first5=Paul J. |last6=Branscomb |first6=Elbert |last7=Kidd |first7=Richard |last8=McGlynn |first8=Shawn |last9=Meier |first9=David H. |last10=Nitschke |first10=Wolfgang |last11=Shibuya |first11=Takazo |last12=Vance |first12=Steve |last13=White |first13=Lauren |last14=Kanik |first14=Isik |journal=Astrobiology |volume=14 |issue=4 |pages=308–343 |pmid=24697642 |pmc=3995032 |bibcode=2014AsBio..14..308R}}</ref> === Hylomorphism === {{Main|Hylomorphism}} [[File:Aristotelian Soul.png|thumb|upright=1.5|The [[Soul#Aristotle|structure of the souls]] of plants, animals, and humans, according to [[Aristotle]]]] Hylomorphism is a theory first expressed by the Greek philosopher [[Aristotle]] (322 BC). The application of hylomorphism to biology was important to Aristotle, and [[Aristotle's biology|biology is extensively covered in his extant writings]]. In this view, everything in the material universe has both matter and form, and the form of a living thing is its [[Soul (spirit)|soul]] (Greek ''psyche'', Latin ''anima''). There are three kinds of souls: the ''vegetative soul'' of plants, which causes them to grow and decay and nourish themselves, but does not cause motion and sensation; the ''animal soul'', which causes animals to move and feel; and the ''rational soul'', which is the source of consciousness and reasoning, which (Aristotle believed) is found only in man.<ref>{{Cite book |title=On the Soul |last=Aristotle |pages=Book II |no-pp=y |title-link=On the Soul }}</ref> Each higher soul has all of the attributes of the lower ones. Aristotle believed that while matter can exist without form, form cannot exist without matter, and that therefore the soul cannot exist without the body.<ref>{{cite book |first1=Don |last1=Marietta |page=104 |title=Introduction to ancient philosophy |publisher=M.E. Sharpe |date=1998 |isbn=978-0-7656-0216-9 |url=https://books.google.com/books?id=Gz-8PsrT32AC |access-date=25 August 2020 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194754/https://books.google.com/books?id=Gz-8PsrT32AC |url-status=live }}</ref> This account is consistent with [[Teleology in biology|teleological explanations of life]], which account for phenomena in terms of purpose or goal-directedness. Thus, the whiteness of the polar bear's coat is explained by its purpose of camouflage. The direction of causality (from the future to the past) is in contradiction with the scientific evidence for natural selection, which explains the consequence in terms of a prior cause. Biological features are explained not by looking at future optimal results, but by looking at the past [[evolutionary history]] of a species, which led to the natural selection of the features in question.<ref name=stewert_williams2010>{{Cite book |first1=Steve |last1=Stewart-Williams |date=2010 |title=Darwin, God and the meaning of life: how evolutionary theory undermines everything you thought you knew of life |publisher=Cambridge University Press |isbn=978-0-521-76278-6 |pages=193–194 |url=https://books.google.com/books?id=KBp69los_-oC&pg=PA193 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194752/https://books.google.com/books?id=KBp69los_-oC&pg=PA193 |url-status=live }}</ref> === Spontaneous generation === {{Main|Spontaneous generation}} Spontaneous generation was the belief that living organisms can form without descent from similar organisms. Typically, the idea was that certain forms such as fleas could arise from inanimate matter such as dust or the supposed seasonal generation of mice and insects from mud or garbage.<ref>{{Cite book |title=Origines Sacrae |last=Stillingfleet |first=Edward |publisher=Cambridge University Press |year=1697 }}</ref> The theory of spontaneous generation was proposed by [[Aristotle]],<ref>{{cite book |author=André Brack |editor=André Brack |title=The Molecular Origins of Life |access-date=7 January 2009 |year=1998 |publisher=Cambridge University Press |isbn=978-0-521-56475-5 |page=[https://archive.org/details/molecularorigins0000brac/page/1 1] |chapter=Introduction |chapter-url=http://assets.cambridge.org/97805215/64755/excerpt/9780521564755_excerpt.pdf |url=https://archive.org/details/molecularorigins0000brac/page/1 }}</ref> who compiled and expanded the work of prior natural philosophers and the various ancient explanations of the appearance of organisms; it was considered the best explanation for two millennia. It was decisively dispelled by the experiments of [[Louis Pasteur]] in 1859, who expanded upon the investigations of predecessors such as [[Francesco Redi]].<ref>{{cite web |last1=Levine |first1=Russell |last2=Evers |first2=Chris |title=The Slow Death of Spontaneous Generation (1668–1859) |url=http://www.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |website=North Carolina State University |publisher=National Health Museum |url-status=dead |archive-url=https://web.archive.org/web/20151009044415/http://www.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |archive-date=9 October 2015 |access-date=6 February 2016 }}</ref><ref>{{Cite book |title=Fragments of Science |last=Tyndall |first=John |publisher=P.F. Collier |year=1905 |volume=2 |location=New York |pages=Chapters IV, XII, and XIII |no-pp=y }}</ref> Disproof of the traditional ideas of spontaneous generation is no longer controversial among biologists.<ref name="Bernal 1967">{{cite book |last=Bernal |first=J.D. |year=1967 |orig-year=Reprinted work by [[Alexander Oparin|A.I. Oparin]] originally published 1924; Moscow: [[Publishing houses in the Soviet Union|The Moscow Worker]] |title=The Origin of Life |url=https://archive.org/details/originoflife0000bern |url-access=registration |series=The Weidenfeld and Nicolson Natural History |others=Translation of Oparin by Ann Synge |location=London |publisher=[[Weidenfeld & Nicolson]] |lccn=67098482}}</ref><ref>{{Cite book |title=Origins of Life: On Earth and in the Cosmos |last=Zubay |first=Geoffrey |publisher=Academic Press |year=2000 |isbn=978-0-12-781910-5 |edition=2nd }}</ref><ref name= "Szathmary">{{cite book |author1=Smith, John Maynard |author2=Szathmary, Eors |title=The Major Transitions in Evolution |publisher=Oxford University Press |location=Oxford Oxfordshire |year=1997 |isbn=978-0-19-850294-4}}</ref> === Vitalism === {{Main|Vitalism}} Vitalism is the belief that there is a non-material life-principle. This originated with [[Georg Ernst Stahl]] (17th century), and remained popular until the middle of the 19th century. It appealed to philosophers such as [[Henri Bergson]], [[Friedrich Nietzsche]], and [[Wilhelm Dilthey]],<ref>{{cite book |first1=Sanford |last1=Schwartz |title=C.S. Lewis on the Final Frontier: Science and the Supernatural in the Space Trilogy |publisher=Oxford University Press |date=2009 |isbn=978-0-19-988839-9 |page=56 |url=https://books.google.com/books?id=4hQLdPtJe9EC&pg=PA56 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194800/https://books.google.com/books?id=4hQLdPtJe9EC&pg=PA56 |url-status=live }}</ref> anatomists like [[Xavier Bichat]], and chemists like [[Justus von Liebig]].<ref name=Wilkinson>{{cite journal |first1=Ian |last1=Wilkinson |title=History of Clinical Chemistry – Wöhler & the Birth of Clinical Chemistry |journal=The Journal of the International Federation of Clinical Chemistry and Laboratory Medicine |volume=13 |issue=4 |year=1998 |url=http://www.ifcc.org/ifccfiles/docs/130304003.pdf |access-date=27 December 2015 |url-status=dead |archive-url=https://web.archive.org/web/20160105031229/http://www.ifcc.org/ifccfiles/docs/130304003.pdf |archive-date=5 January 2016 }}</ref> Vitalism included the idea that there was a fundamental difference between organic and inorganic material, and the belief that [[organic material]] can only be derived from living things. This was disproved in 1828, when [[Friedrich Wöhler]] prepared [[urea]] from inorganic materials.<ref>{{cite journal |title=Ueber künstliche Bildung des Harnstoffs |author=Friedrich Wöhler |journal=[[Annalen der Physik und Chemie]] |volume=88 |issue=2 |pages=253–256 |year=1828 |doi=10.1002/andp.18280880206 |url=http://gallica.bnf.fr/ark:/12148/bpt6k15097k/f261.chemindefer |bibcode=1828AnP....88..253W |url-status=live |archive-url=https://web.archive.org/web/20120110094705/http://gallica.bnf.fr/ark:/12148/bpt6k15097k/f261.chemindefer |archive-date=10 January 2012 |author-link=Friedrich Wöhler }}</ref> This [[Wöhler synthesis]] is considered the starting point of modern [[organic chemistry]]. It is of historical significance because for the first time an [[organic compound]] was produced in [[inorganic compound|inorganic]] reactions.<ref name=Wilkinson/> During the 1850s [[Hermann von Helmholtz]], anticipated by [[Julius Robert von Mayer]], demonstrated that no energy is lost in muscle movement, suggesting that there were no "vital forces" necessary to move a muscle.<ref>{{cite book |first1=Anson |last1=Rabinbach |title=The Human Motor: Energy, Fatigue, and the Origins of Modernity |publisher=University of California Press |date=1992 |isbn=978-0-520-07827-7 |pages=124–125 |url=https://books.google.com/books?id=e5ZBNv-zTlQC&pg=PA124 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194755/https://books.google.com/books?id=e5ZBNv-zTlQC&pg=PA124 |url-status=live }}</ref> These results led to the abandonment of scientific interest in vitalistic theories, especially after [[Eduard Buchner]]'s demonstration that alcoholic fermentation could occur in cell-free extracts of yeast.<ref>{{cite book | isbn= 978-8437-033280 | title= New Beer in an Old Bottle. Eduard Buchner and the Growth of Biochemical Knowledge | editor= Cornish-Bowden Athel | year=1997 | publisher = Universitat de València | place=Valencia, Spain}}</ref> Nonetheless, belief still exists in [[Pseudoscience|pseudoscientific]] theories such as [[homoeopathy]], which interprets diseases and sickness as caused by disturbances in a hypothetical vital force or life force.<ref>{{cite web |url=http://www.ncahf.org/pp/homeop.html |title=NCAHF Position Paper on Homeopathy |date=February 1994 |publisher=National Council Against Health Fraud |access-date=12 June 2012 |archive-date=25 December 2018 |archive-url=https://web.archive.org/web/20181225185228/https://www.ncahf.org/pp/homeop.html |url-status=live }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. 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