Aristotle

== Natural philosophy ==
Aristotle's "natural philosophy" spans a wide range of natural phenomena including those now covered by physics, biology and other natural sciences.{{sfn| Wildberg | 2016}} In Aristotle's terminology, "natural philosophy" is a branch of philosophy examining the phenomena of the natural world, and includes fields that would be regarded today as physics, biology and other natural sciences. Aristotle's work encompassed virtually all facets of intellectual inquiry. Aristotle makes philosophy in the broad sense coextensive with reasoning, which he also would describe as "science". However, his use of the term ''science'' carries a different meaning than that covered by the term "scientific method". For Aristotle, "all science (''dianoia'') is either practical, poetical or theoretical" (''Metaphysics'' 1025b25). His practical science includes ethics and politics; his poetical science means the study of fine arts including poetry; his theoretical science covers physics, mathematics and metaphysics.{{sfn|Wildberg|2016}}

=== Physics ===
[[File:Four Classical Elements in Burning Log.svg| thumb | The four [[classical element]]s (fire, air, water, earth) of [[Empedocles]] and Aristotle illustrated with a burning log. The log releases all four elements as it is destroyed.]]
{{Main|Aristotelian physics}}

==== Five elements ====
{{Main|Classical element}}

In his ''[[On Generation and Corruption]]'', Aristotle related each of the four elements proposed earlier by [[Empedocles]], [[Earth (classical element)|earth]], [[Water (classical element)|water]], [[Air (classical element)|air]], and [[Fire (classical element)|fire]], to two of the four sensible qualities, hot, cold, wet, and dry. In the Empedoclean scheme, all matter was made of the four elements, in differing proportions. Aristotle's scheme added the heavenly [[Aether (classical element)|aether]], the divine substance of the [[Celestial spheres|heavenly spheres]], stars and planets.{{sfn|Lloyd|1968|pages=133–139, 166–169}}

{| class="wikitable"
|+ [[Classical element|Aristotle's elements]]{{sfn|Lloyd|1968|pages=133–139, 166–169}}
! Element !!{{font color|red|Hot}}/{{font color|blue|Cold}} !!{{font color|green|Wet}}/{{font color|brown|Dry}} !! Motion !! Modern [[State of matter|state<br />of matter]]
|-
|'''[[Earth (classical element)|Earth]]'''||{{font color|blue|Cold}}||{{font color|brown|Dry}}||Down||[[Solid]]
|-
|'''[[Water (classical element)|Water]]'''||{{font color|blue|Cold}}||{{font color|green|Wet}}||Down||[[Liquid]]
|-
|'''[[Air (classical element)|Air]]'''||{{font color|red|Hot}}||{{font color|green|Wet}}||Up||[[Gas]]
|-
|'''[[Fire (classical element)|Fire]]'''||{{font color|red|Hot}}||{{font color|brown|Dry}}||Up||[[Plasma (physics)|Plasma]]
|-
|'''[[Aether (classical element)|Aether]]'''||(divine<br />substance)||—||Circular<br />(in heavens)||[[Vacuum]]
|}

==== Motion ====
{{further | History of classical mechanics}}

Aristotle describes two kinds of motion: "violent" or "unnatural motion", such as that of a thrown stone, in the ''Physics'' (254b10), and "natural motion", such as of a falling object, in ''On the Heavens'' (300a20). In violent motion, as soon as the agent stops causing it, the motion stops also: in other words, the natural state of an object is to be at rest,{{sfn| Allain | 2016}}{{efn-ua | Rhett Allain notes that [[Newton's First Law]] is "essentially a direct reply to Aristotle, that the natural state is ''not to change'' motion.{{sfn| Allain | 2016}}}} since Aristotle does not address [[friction]].{{sfn| Drabkin | 1938 | pp=60–84}} With this understanding, it can be observed that, as Aristotle stated, heavy objects (on the ground, say) require more force to make them move; and objects pushed with greater force move faster.{{sfn| Susskind | 2011}}{{efn-ua | Leonard Susskind comments that Aristotle had clearly never gone [[ice skating]] or he would have seen that it takes force to stop an object.{{sfn| Susskind | 2011}}}} This would imply the equation{{sfn| Susskind | 2011}}

:: <math>F=mv</math>,

incorrect in modern physics.{{sfn| Susskind | 2011}}

Natural motion depends on the element concerned: the aether naturally moves in a circle around the heavens,{{efn-ua | For heavenly bodies like the Sun, Moon, and stars, the observed motions are "to a very good approximation" circular around the Earth's centre, (for example, the apparent rotation of the sky because of the rotation of the Earth, and the rotation of the moon around the Earth) as Aristotle stated.{{sfn| Rovelli | 2015 | pp=23–40}}}} while the 4 Empedoclean elements move vertically up (like fire, as is observed) or down (like earth) towards their natural resting places.{{sfn| Rovelli | 2015 | pp=23–40}}{{sfn| Drabkin | 1938 | pp=60–84}}{{efn-ua | Drabkin quotes numerous passages from ''Physics'' and ''On the Heavens'' (''De Caelo'') which state Aristotle's laws of motion.{{sfn| Drabkin | 1938 | pp=60–84}}}}

[[File:Aristotle's laws of motion.svg| thumb | upright=1.5 | Aristotle's laws of motion. In ''[[Physics (Aristotle)|Physics]]'' he states that objects fall at a speed proportional to their weight and inversely proportional to the density of the fluid they are immersed in.{{sfn| Drabkin | 1938 | pp=60–84}} This is a correct approximation for objects in Earth's gravitational field moving in air or water.{{sfn| Rovelli | 2015 | pp=23–40}}]]

In the ''Physics'' (215a25), Aristotle effectively states a quantitative law, that the speed, v, of a falling body is proportional (say, with constant c) to its weight, W, and inversely proportional to the density,{{efn-ua | Drabkin agrees that density is treated quantitatively in this passage, but without a sharp definition of density as weight per unit volume.{{sfn| Drabkin | 1938 | pp=60–84}}}} ρ, of the fluid in which it is falling:;{{sfn| Rovelli | 2015 | pp=23–40}}{{sfn| Drabkin | 1938 | pp=60–84}}

:: <math>v=c\frac{W}{\rho}</math>

Aristotle implies that in a [[vacuum]] the speed of fall would become infinite, and concludes from this apparent absurdity that a vacuum is not possible.{{sfn| Rovelli | 2015 | pp=23–40}}{{sfn| Drabkin | 1938 | pp=60–84}} Opinions have varied on whether Aristotle intended to state quantitative laws. Henri Carteron held the "extreme view"{{sfn| Drabkin | 1938 | pp=60–84}} that Aristotle's concept of force was basically qualitative,{{sfn| Carteron | 1923 | pages=1–32 and passim}} but other authors reject this.{{sfn| Drabkin | 1938 | pp=60–84}}

[[Archimedes]] corrected Aristotle's theory that bodies move towards their natural resting places; metal boats can float if they [[Archimedes' principle|displace enough water]]; floating depends in Archimedes' scheme on the mass and volume of the object, not, as Aristotle thought, its elementary composition.{{sfn| Rovelli | 2015 | pp=23–40}}

Aristotle's writings on motion remained influential until the [[Early Modern]] period. [[John Philoponus]] (in [[Late antiquity]]) and [[Galileo Galilei|Galileo]] (in [[Early modern period]]) are said to have shown by experiment that Aristotle's claim that a heavier object falls faster than a lighter object is incorrect.{{sfn| Wildberg | 2016}} A contrary opinion is given by [[Carlo Rovelli]], who argues that Aristotle's physics of motion is correct within its domain of validity, that of objects in the [[Earth]]'s gravitational field immersed in a fluid such as air. In this system, heavy bodies in steady fall indeed travel faster than light ones (whether friction is ignored, or not{{sfn| Rovelli | 2015 | pp=23–40}}), and they do fall more slowly in a denser medium.{{sfn| Susskind | 2011}}{{efn-ua | Philoponus and Galileo correctly objected that for the transient phase (still increasing in speed) with heavy objects falling a short distance, the law does not apply: Galileo used balls on a short incline to show this. Rovelli notes that "Two heavy balls with the same shape and different weight do fall at different speeds from an aeroplane, confirming Aristotle's theory, not Galileo's."{{sfn| Rovelli | 2015 | pp=23–40}}}}

Newton's "forced" motion corresponds to Aristotle's "violent" motion with its external agent, but Aristotle's assumption that the agent's effect stops immediately it stops acting (e.g., the ball leaves the thrower's hand) has awkward consequences: he has to suppose that surrounding fluid helps to push the ball along to make it continue to rise even though the hand is no longer acting on it, resulting in the Medieval [[theory of impetus]].{{sfn| Rovelli | 2015 | pp=23–40}}

==== Four causes ====
{{Main|Four causes}}
[[File:Aristotle's Four Causes of a Table.svg| thumb | upright=1.5 | Aristotle argued by analogy with woodwork that a thing takes its form from [[four causes]]: in the case of a table, the wood used ([[material cause]]), its design ([[formal cause]]), the tools and techniques used ([[efficient cause]]), and its decorative or practical purpose ([[final cause]]).{{sfn| Leroi | 2015 | pages=88–90}}]]

Aristotle suggested that the reason for anything coming about can be attributed to four different types of simultaneously active factors. His term ''aitia'' is traditionally translated as "cause", but it does not always refer to temporal sequence; it might be better translated as "explanation", but the traditional rendering will be employed here.{{sfn| Lloyd | 1996 | pages=96–100, 106–107}}{{sfn| Hankinson | 1998 | page=159}}
* [[Material cause]] describes the material out of which something is composed. Thus the material cause of a table is wood. It is not about action. It does not mean that one domino knocks over another domino.{{sfn| Lloyd | 1996 | pages=96–100, 106–107}}
* The [[formal cause]] is its form, i.e., the arrangement of that matter. It tells one what a thing is, that a thing is determined by the definition, form, pattern, essence, whole, synthesis or archetype. It embraces the account of causes in terms of fundamental principles or general laws, as the whole (i.e., macrostructure) is the cause of its parts, a relationship known as the whole-part causation. Plainly put, the formal cause is the idea in the mind of the sculptor that brings the sculpture into being. A simple example of the formal cause is the mental image or idea that allows an artist, architect, or engineer to create a drawing.{{sfn| Lloyd | 1996 | pages=96–100, 106–107}}
* The [[efficient cause]] is "the primary source", or that from which the change under consideration proceeds. It identifies 'what makes of what is made and what causes change of what is changed' and so suggests all sorts of agents, non-living or living, acting as the sources of change or movement or rest. Representing the current understanding of causality as the relation of cause and effect, this covers the modern definitions of "cause" as either the agent or agency or particular events or states of affairs. In the case of two dominoes, when the first is knocked over it causes the second also to fall over.{{sfn| Lloyd | 1996 | pages=96–100, 106–107}} In the case of animals, this agency is a combination of [[developmental biology|how it develops from the egg]], and [[physiology|how its body functions]].{{sfn| Leroi | 2015 | pages=91–92, 369–373}}
* The [[final cause]] (''telos'') is its purpose, the reason why a thing exists or is done, including both purposeful and instrumental actions and activities. The final cause is the purpose or function that something is supposed to serve. This covers modern ideas of motivating causes, such as volition.{{sfn| Lloyd | 1996 | pages=96–100, 106–107}} In the case of living things, it implies [[adaptation]] to a particular way of life.{{sfn| Leroi | 2015 | pages=91–92, 369–373}}

==== Optics ====
{{further | History of optics}}

Aristotle describes experiments in [[optics]] using a [[camera obscura]] in ''[[Problems (Aristotle)|Problems]]'', book 15. The apparatus consisted of a dark chamber with a small [[aperture]] that let light in. With it, he saw that whatever shape he made the hole, the sun's image always remained circular. He also noted that increasing the distance between the aperture and the image surface magnified the image.{{sfn| Lahanas}}

==== Chance and spontaneity ====
{{further | Accident (philosophy)}}

According to Aristotle, spontaneity and chance are causes of some things, distinguishable from other types of cause such as simple necessity. Chance as an incidental cause lies in the realm of [[Accident (philosophy)|accidental things]], "from what is spontaneous". There is also more a specific kind of chance, which Aristotle names "luck", that only applies to people's moral choices.{{sfn| Physics | p=2.6}}{{sfn| Miller | 1973 | pp=204–213}}

=== Astronomy ===
{{further | History of astronomy}}

In [[astronomy]], Aristotle refuted [[Democritus]]'s claim that the [[Milky Way]] was made up of "those stars which are shaded by the earth from the sun's rays," pointing out partly correctly that if "the size of the sun is greater than that of the earth and the distance of the stars from the earth many times greater than that of the sun, then... the sun shines on all the stars and the earth screens none of them."{{sfn| Meteorology | p=1. 8}} He also wrote descriptions of comets, including the [[Great Comet of 371 BC]].{{sfn| Meteorology}}

=== Geology and natural sciences ===
{{further | History of geology}}
[[File:Aerial image of Stromboli (view from the northeast).jpg| thumb | Aristotle noted that the ground level of the [[Aeolian islands]] changed before a [[volcanic eruption]].]]
Aristotle was one of the first people to record any [[geology|geological]] observations. He stated that [[Uniformitarianism|geological change]] was too slow to be observed in one person's lifetime.{{sfn| Moore | 1956 | page=13}}{{sfn| Meteorology | p=Book 1, Part 14}}
The geologist [[Charles Lyell]] noted that Aristotle described such change, including "lakes that had dried up" and "deserts that had become watered by rivers", giving as examples the growth of the [[Nile delta]] since the time of [[Homer]], and "the upheaving of one of the [[Aeolian islands]], previous to a [[volcanic eruption]]."'{{sfn| Lyell | 1832 | page=17}}

''Meteorologica'' lends its name to the modern study of meteorology, but its modern usage diverges from the content of Aristotle's ancient treatise on [[meteors]]. The ancient Greeks did use the term for a range of atmospheric phenomena, but also for [[earthquakes]] and volcanic eruptions. Aristotle proposed that the cause of earthquakes was a gas or vapor (''anathymiaseis'') that was trapped inside the earth and trying to escape, following other Greek authors [[Anaxagoras]], [[Empedocles]] and [[Democritus]].<ref>{{cite book |last1=Udias |first1=Agustin |last2=Buforn |first2=Elisa |title=Principles of Seismology |date=2018 |publisher=Cambridge University Press |page=1}}</ref>

Aristotle also made many observations about the hydrologic cycle. For example, he made some of the earliest observations about desalination: he observed early – and correctly – that when seawater is heated, freshwater evaporates and that the oceans are then replenished by the cycle of rainfall and river runoff ("I have proved by experiment that salt water evaporated forms fresh and the vapor does not when it condenses condense into sea water again.")<ref>{{cite book |last=Aristotle|translator-last=Lee|translator-first=H.D.P.|title=Meteorologica, Chapter II |year=1952 |publisher=[[Harvard University Press]] |location=Cambridge, Massachusetts |page=156 |edition=Loeb Classical Library |url=http://archive.org/details/L397AristotleMeteorologica |access-date=22 January 2021}}</ref>

=== Biology ===
{{Main|Aristotle's biology}}
[[File:Tremoctopus violaceus5.jpg| thumb | upright | Among many pioneering zoological observations, Aristotle described the reproductive [[hectocotylus|hectocotyl arm]] of the [[octopus]] (bottom left).]]

==== Empirical research ====
Aristotle was the first person to study biology systematically,{{sfn| Leroi | 2015 | page=7}} and biology forms a large part of his writings. He spent two years observing and describing the zoology of [[Lesbos]] and the surrounding seas, including in particular the Pyrrha lagoon in the centre of Lesbos.{{sfn| Leroi | 2015 | page=14}}{{sfn| Thompson | 1910 | page=Prefatory Note}} His data in ''[[History of Animals]]'', ''[[Generation of Animals]]'', ''[[Movement of Animals]]'', and ''[[Parts of Animals]]'' are assembled from his own observations,<ref>{{Cite web|url=https://www.independent.co.uk/arts-entertainment/books/reviews/darwins-ghosts-by-rebecca-stott-7808310.html|title=Darwin's Ghosts, By Rebecca Stott
|website=independent.co.uk|date=2 June 2012
|access-date=19 June 2012}}</ref> statements given by people with specialized knowledge, such as beekeepers and fishermen, and less accurate accounts provided by travellers from overseas.{{sfn| Leroi | 2015 | pages=196, 248}} His apparent emphasis on animals rather than plants is a historical accident: his works on [[botany]] have been lost, but two books on plants by his pupil Theophrastus have survived.{{sfn| Day | 2013 | pp=5805–5816}}

Aristotle reports on the sea-life visible from observation on Lesbos and the catches of fishermen. He describes the [[catfish]], [[electric ray]], and [[frogfish]] in detail, as well as [[cephalopod]]s such as the [[octopus]] and [[paper nautilus]]. His description of the [[hectocotylus|hectocotyl arm]] of cephalopods, used in sexual reproduction, was widely disbelieved until the 19th century.{{sfn| Leroi | 2015 | pages=66–74, 137}} He gives accurate descriptions of the four-chambered fore-stomachs of [[ruminant]]s,{{sfn| Leroi | 2015 | pages=118–119}} and of the [[Ovoviviparity|ovoviviparous]] embryological development of the [[hound shark]].{{sfn| Leroi | 2015 | page=73}}

He notes that an animal's structure is well matched to function so birds like the [[heron]] (which live in marshes with soft mud and live by catching fish) have a long neck, long legs, and a sharp spear-like beak, whereas [[duck]]s that swim have short legs and webbed feet.{{sfn| Leroi | 2015 | pages=135–136}} [[Charles Darwin|Darwin]], too, noted these sorts of differences between similar kinds of animal, but unlike Aristotle used the data to come to the theory of [[evolution]].{{sfn| Leroi | 2015 | page=206}} Aristotle's writings can seem to modern readers close to implying evolution, but while Aristotle was aware that new mutations or [[Hybridisation (biology)|hybridizations]] could occur, he saw these as rare accidents. For Aristotle, accidents, like heat waves in winter, must be considered distinct from natural causes. He was thus critical of Empedocles's materialist theory of a "survival of the fittest" origin of living things and their organs, and ridiculed the idea that accidents could lead to orderly results.{{sfn| Sedley | 2007 | page=189}} To put his views into modern terms, he nowhere says that different species can have a [[common descent|common ancestor]], or that one kind can [[speciation|change into another]], or that kinds can become [[extinction|extinct]].{{sfn| Leroi | 2015 | page=273}}

==== Scientific style ====
[[File:Two of Aristotle's Growth Laws.svg| thumb | left | upright=1.4 | Aristotle inferred growth laws from his observations on animals, including that [[brood size]] decreases with body mass, whereas [[gestation]] period increases. He was correct in these predictions, at least for mammals: data are shown for mouse and elephant.]]

Aristotle did not do experiments in the modern sense.{{sfn| Taylor | 1922 | page=42}} He used the ancient Greek term ''pepeiramenoi'' to mean observations, or at most investigative procedures like dissection.{{sfn| Leroi | 2015 | pages=361–365}} In ''Generation of Animals'', he finds a fertilized hen's egg of a suitable stage and opens it to see the embryo's heart beating inside.{{sfn| Leroi | 2011}}{{sfn| Leroi | 2015 | pages=197–200}}

Instead, he practiced a different style of science: systematically gathering data, discovering patterns common to whole groups of animals, and inferring possible causal explanations from these.{{sfn| Leroi | 2015 | pages=365–368}}{{sfn| Taylor | 1922 | page=49}} This style is common in modern biology when large amounts of data become available in a new field, such as [[genomics]]. It does not result in the same certainty as experimental science, but it sets out testable hypotheses and constructs a narrative explanation of what is observed. In this sense, [[Aristotle's biology]] is scientific.{{sfn| Leroi | 2015 | pages=365–368}}

From the data he collected and documented, Aristotle inferred quite a number of [[biological rules|rules]] relating the life-history features of the live-bearing tetrapods (terrestrial placental mammals) that he studied. Among these correct predictions are the following. Brood size decreases with (adult) body mass, so that an elephant has fewer young (usually just one) per brood than a mouse. [[Life expectancy|Lifespan]] increases with [[gestation period]], and also with body mass, so that elephants live longer than mice, have a longer period of gestation, and are heavier. As a final example, [[fecundity]] decreases with lifespan, so long-lived kinds like elephants have fewer young in total than short-lived kinds like mice.{{sfn| Leroi | 2015 | page=408}}{{Clear}}

==== Classification of living things ====

{{further|Scala naturae}}

[[File:Scyliorhinus retifer embryo.JPG|thumb |Aristotle recorded that the [[embryo]] of [[Mustelus canis|<!--a different species shown-->a dogfish]] was attached by a cord to a kind of placenta (the [[yolk sac]]), like a higher animal; this formed an exception to the linear scale from highest to lowest.{{sfn|Leroi|2015|pages=72–74}}]]

Aristotle distinguished about 500 species of [[animal]]s,{{sfn|Bergstrom|Dugatkin|2012|page=35}}{{sfn|Rhodes|1974|page=7}} arranging these in the ''History of Animals'' in a graded scale of perfection, a nonreligious version of the ''[[scala naturae]]'', with man at the top. His system had eleven grades of animal, from highest potential to lowest, expressed in their form at birth: the highest gave [[viviparity|live birth]] to hot and wet creatures, the lowest laid cold, dry mineral-like eggs. Animals came above [[plant]]s, and these in turn were above minerals.{{sfn|Mayr|1982|pages=201–202}}{{sfn|Lovejoy|1976}} He grouped what the modern zoologist would call [[vertebrate]]s as the hotter "animals with blood", and below them the colder [[invertebrate]]s as "animals without blood". Those with blood were divided into the live-bearing ([[mammal]]s), and the egg-laying ([[bird]]s, [[reptile]]s, [[fish]]). Those without blood were insects, crustacea (non-shelled – cephalopods, and [[crustacea|shelled]]) and the hard-shelled [[mollusc]]s ([[bivalve]]s and [[gastropod]]s). He recognised that animals did not exactly fit into a linear scale, and noted various exceptions, such as that sharks had a [[placenta]] like the tetrapods. To a modern biologist, the explanation, not available to Aristotle,<!--Leroi |p= 113--> is [[convergent evolution]].{{sfn|Leroi|2015|pages=111–119}} Philosophers of science have generally concluded that Aristotle was not interested in taxonomy,<ref>{{cite book |last=Lennox |first=James G. |title=Aristotle's Philosophy of Biology: Studies in the Origins of Life Science |date=2001 |publisher=[[Cambridge University Press]] |location=Cambridge |isbn=0-521-65976-0 |pages=346}}</ref><ref>{{cite journal |last1=Sandford |first1=Stella |title=From Aristotle to Contemporary Biological Classification: What Kind of Category is "Sex"? |journal=Redescriptions: Political Thought, Conceptual History and Feminist Theory |date=3 December 2019 |volume=22 |issue=1 |pages=4–17 |doi=10.33134/rds.314 |s2cid=210140121 |language=en |issn=2308-0914|doi-access=free }}</ref> but zoologists who studied this question in the early 21st century think otherwise.<ref>{{cite journal |last1=Voultsiadou |first1=Eleni |last2=Vafidis |first2=Dimitris |title=Marine invertebrate diversity in Aristotle's zoology |journal=Contributions to Zoology |date=1 January 2007 |volume=76 |issue=2 |pages=103–120 |doi=10.1163/18759866-07602004 |s2cid=55152069 |url=https://doi.org/10.1163/18759866-07602004 |language=en |issn=1875-9866}}</ref><ref>{{cite journal |last1=von Lieven |first1=Alexander Fürst |last2=Humar |first2=Marcel |title=A Cladistic Analysis of Aristotle's Animal Groups in the "Historia animalium" |journal=History and Philosophy of the Life Sciences |date=2008 |volume=30 |issue=2 |pages=227–262 |jstor=23334371 |pmid=19203017 |url=https://www.jstor.org/stable/23334371 |issn=0391-9714}}</ref><ref>{{cite journal |last1=Laurin |first1=Michel |last2=Humar |first2=Marcel |title=Phylogenetic signal in characters from Aristotle's History of Animals |journal=Comptes Rendus Palevol |date=2022 |volume=21 |issue=1 |pages=1–16 |doi=10.5852/cr-palevol2022v21a1 |s2cid=245863171 |language=fr|doi-access=free }}</ref> He believed that purposive final causes guided all natural processes; this [[teleological]] view justified his observed data as an expression of formal design.{{sfn|Mason|1979|pp=43–44}}

{|class="wikitable" style="font-size: 80%;"
|+ Aristotle's ''[[Scala naturae]]'' (highest to lowest)
! Group !! Examples<br/>(given by Aristotle) !! Blood !! Legs !! Souls<br/>(Rational,<br/>Sensitive,<br/>Vegetative) !! Qualities<br/>({{font color|red|Hot}}–{{font color|blue|Cold}},<br/>{{font color|green|Wet}}–{{font color|brown|Dry}})
|-
|Man||Man||with&nbsp;blood||2 legs||R, S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Mammal|Live-bearing tetrapods]]||Cat, [[hare]]||with&nbsp;blood||4 legs||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Cetaceans]]||[[Dolphin]], [[whale]]||with&nbsp;blood||none||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}
|-
|[[Birds]]||[[Bee-eater]], [[nightjar]]||with&nbsp;blood||2 legs||S, V||{{font color|red|Hot}}, {{font color|green|Wet}}, except {{font color|brown|Dry}} eggs
|-
|[[Reptile|Egg-laying tetrapods]]||[[Chameleon]], [[crocodile]]||with&nbsp;blood||4 legs||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except scales, eggs
|-
|[[Snakes]]||Water snake, [[Ottoman viper]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except scales, eggs
|-
|Egg-laying [[fish]]es||[[Sea bass]], [[Sparisoma cretense|parrotfish]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}, including eggs
|-
|(Among the egg-laying fishes):<br />placental [[selachian]]s||[[Shark]], [[Skate (fish)|skate]]||with&nbsp;blood||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}, but [[placenta]] like tetrapods
|-
|[[Crustaceans]]||[[Shrimp]], [[crab]]||without||many legs||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} except shell
|-
|[[Cephalopods]]||[[Squid]], [[octopus]]||without||tentacles||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}}
|-
|[[Mollusc|Hard-shelled animals]]||[[Cockle (bivalve)|Cockle]], [[Charonia variegata|trumpet snail]]||without||none||S, V||{{font color|blue|Cold}}, {{font color|brown|Dry}} (mineral shell)
|-
|Larva-bearing insects||[[Ant]], [[cicada]]||without||6 legs||S, V||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|-
|[[Spontaneous generation|Spontaneously generating]]||[[Sponges]], [[worm]]s||without||none||S, V||{{font color|blue|Cold}}, {{font color|green|Wet}} or {{font color|brown|Dry}}, from earth
|-
|[[Plants]]||[[Common fig|Fig]]||without||none||V||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|-
|[[Mineral]]s||Iron||without||none||none||{{font color|blue|Cold}}, {{font color|brown|Dry}}
|}

=== Psychology ===
==== Soul ====
{{further | On the Soul}}
[[File:Aristotelian Soul.png| thumb | upright=1.5 | Aristotle proposed a three-part [[Soul#Aristotle|structure for souls]] of plants, animals, and humans, making humans unique in having all three types of soul.]]

Aristotle's [[psychology]], given in his treatise ''[[On the Soul]]'' (''peri psychēs''), posits three kinds of [[soul]] ("psyches"): the vegetative soul, the sensitive soul, and the rational soul. Humans have all three. The vegetative soul is concerned with growth and nourishment. The sensitive soul experiences sensations and movement. The unique part of the human, rational soul is its ability to receive forms of other things and to compare them using the ''[[Nous#Aristotle|nous]]'' (intellect) and ''logos'' (reason).{{sfn| Leroi | 2015 | pages=156–163}}

For Aristotle, the soul is the [[Hylomorphism#Body–soul hylomorphism|form]] of a living being. Because all beings are composites of form and matter, the form of living beings is that which endows them with what is specific to living beings, e.g. the ability to initiate movement (or in the case of plants, growth and transformations, which Aristotle considers types of movement).{{sfn| Shields | 2016}} In contrast to earlier philosophers, but in accordance with the Egyptians, he placed the rational soul in the heart, rather than the brain.{{sfn| Mason | 1979 | p=45}} Notable is Aristotle's division of sensation and thought, which generally differed from the concepts of previous philosophers, with the exception of [[Alcmaeon of Croton|Alcmaeon]].{{sfn| Guthrie | 2010 | p=348}}

In ''On the Soul'', Aristotle famously criticizes Plato's theory of the soul and develops his own in response. The first criticism is against Plato's view of the soul in the ''Timaeus'' that the soul takes up space and is able to come into physical contact with bodies.<ref>''On the Soul'' I.3 406b26-407a10. For some scholarship, see Carter, Jason W. 2017. 'Aristotle's Criticism of Timaean Psychology' ''Rhizomata'' 5: 51–78 and Douglas R. Campbell. 2022. "Located in Space: Plato's Theory of Psychic Motion" ''Ancient Philosophy'' 42 (2): 419–442.</ref> 20th-century scholarship overwhelmingly opposed Aristotle's interpretation of Plato and maintained that he had misunderstood him.<ref>For instance, W.D. Ross argued that Aristotle "may well be criticized as having taken [Plato's] myth as if it were sober prose." See Ross, William D. ed. 1961. ''Aristotle: De Anima''. Oxford: Oxford University Press. The quotation is from page 189.</ref> Today's scholars have tended to re-assess Aristotle's interpretation and been more positive about it.<ref>See, e.g., Douglas R. Campbell, "Located in Space: Plato's Theory of Psychic Motion," ''Ancient Philosophy'' 42 (2): 419–442. 2022.</ref> Aristotle's other criticism is that Plato's view of reincarnation entails that it is possible for a soul and its body to be mis-matched; in principle, Aristotle alleges, any soul can go with any body, according to Plato's theory.<ref>''On the Soul'' I.3''.''407b14–27. Christopher Shields summarizes it thus: "We might think that an old leather-bound edition of Machiavelli's ''The Prince'' could come to bear the departed soul of Richard Nixon. Aristotle regards this sort of view as worthy of ridicule.” See Shields, C. 2016. ''Aristotle: De Anima''. Oxford: Oxford University Press. The quotation is from page 133.</ref> Aristotle's claim that the soul is the form of a living being eliminates that possibility and thus rules out reincarnation.<ref>There's a large scholarly discussion of this dialectic between Plato and Aristotle here: Douglas R. Campbell, "The Soul's Tool: Plato on the Usefulness of the Body," ''Elenchos'' 43 (1): 7–27. 2022.</ref>

==== Memory ====
According to Aristotle in ''On the Soul'', memory is the ability to hold a perceived experience in the mind and to distinguish between the internal "appearance" and an occurrence in the past.{{sfn| Bloch | 2007 | p=12}} In other words, a memory is a mental picture ([[wikt:phantasm|phantasm]]) that can be recovered. Aristotle believed an impression is left on a semi-fluid bodily organ that undergoes several changes in order to make a memory. A memory occurs when [[stimulus (psychology)|stimuli]] such as sights or sounds are so complex that the nervous system cannot receive all the impressions at once. These changes are the same as those involved in the operations of sensation, Aristotelian {{Avoid wrap|'[[common sense]]'}}, and thinking.{{sfn| Bloch | 2007 | p=61}}{{sfn| Carruthers | 2007 | p=16}}

Aristotle uses the term 'memory' for the actual retaining of an experience in the impression that can develop from sensation, and for the intellectual anxiety that comes with the impression because it is formed at a particular time and processing specific contents. Memory is of the past, prediction is of the future, and sensation is of the present. Retrieval of impressions cannot be performed suddenly. A transitional channel is needed and located in past experiences, both for previous experience and present experience.{{sfn| Bloch | 2007 | p=25}}

Because Aristotle believes people receive all kinds of sense perceptions and perceive them as impressions, people are continually weaving together new impressions of experiences. To search for these impressions, people search the memory itself.{{sfn| Warren | 1921 | p=30}} Within the memory, if one experience is offered instead of a specific memory, that person will reject this experience until they find what they are looking for. Recollection occurs when one retrieved experience naturally follows another. If the chain of "images" is needed, one memory will stimulate the next. When people recall experiences, they stimulate certain previous experiences until they reach the one that is needed.{{sfn| Warren | 1921 | p=25}} Recollection is thus the self-directed activity of retrieving the information stored in a memory impression.{{sfn| Carruthers | 2007 | p=19}} Only humans can remember impressions of intellectual activity, such as numbers and words. Animals that have perception of time can retrieve memories of their past observations. Remembering involves only perception of the things remembered and of the time passed.{{sfn| Warren | 1921 | p=296}}

[[File:Aristotle Senses Perception Memory Dreams Action.svg| thumb | upright=2.25 | Senses, perception, memory, dreams, action in Aristotle's psychology. Impressions are stored in the [[sensorium]] (the heart), linked by his [[laws of association]] (similarity, contrast, and [[Contiguity (psychology)|contiguity]]).]]

Aristotle believed the chain of thought, which ends in recollection of certain impressions, was connected systematically in relationships such as similarity, contrast, and [[Contiguity (psychology)|contiguity]], described in his [[laws of association]]. Aristotle believed that past experiences are hidden within the mind. A force operates to awaken the hidden material to bring up the actual experience. According to Aristotle, association is the power innate in a mental state, which operates upon the unexpressed remains of former experiences, allowing them to rise and be recalled.{{sfn| Warren | 1921 | p=259}}{{sfn | Sorabji | 2006 | p=54}}

==== Dreams ====
{{further | Dream#Other}}

Aristotle describes sleep in ''On Sleep and Wakefulness''.{{sfn| Holowchak | 1996 | pp=405–423}} Sleep takes place as a result of overuse of the senses{{sfn| Shute | 1941 | pages=115–118}} or of digestion,{{sfn| Holowchak | 1996 | pp=405–23}} so it is vital to the body.{{sfn| Shute | 1941 | pages=115–118}} While a person is asleep, the critical activities, which include thinking, sensing, recalling and remembering, do not function as they do during wakefulness. Since a person cannot sense during sleep, they cannot have desire, which is the result of sensation. However, the senses are able to work during sleep,{{sfn| Shute | 1941 | pages=115–18}} albeit differently,{{sfn| Holowchak | 1996 | pp=405–423}} unless they are weary.{{sfn| Shute | 1941 | pages=115–118}}

Dreams do not involve actually sensing a stimulus. In dreams, sensation is still involved, but in an altered manner.{{sfn| Shute | 1941 | pages=115–118}} Aristotle explains that when a person stares at a moving stimulus such as the waves in a body of water, and then looks away, the next thing they look at appears to have a wavelike motion. When a person perceives a stimulus and the stimulus is no longer the focus of their attention, it leaves an impression.{{sfn| Holowchak | 1996 | pp=405–423}} When the body is awake and the senses are functioning properly, a person constantly encounters new stimuli to sense and so the impressions of previously perceived stimuli are ignored.{{sfn| Shute | 1941 | pages=115–118}} However, during sleep the impressions made throughout the day are noticed as there are no new distracting sensory experiences.{{sfn| Holowchak | 1996 | pp=405–423}} So, dreams result from these lasting impressions. Since impressions are all that are left and not the exact stimuli, dreams do not resemble the actual waking experience.{{sfn| Modrak | 2009 | pp=169–181}} During sleep, a person is in an altered state of mind. Aristotle compares a sleeping person to a person who is overtaken by strong feelings toward a stimulus. For example, a person who has a strong infatuation with someone may begin to think they see that person everywhere because they are so overtaken by their feelings. Since a person sleeping is in a suggestible state and unable to make judgements, they become easily deceived by what appears in their dreams, like the infatuated person.{{sfn| Holowchak | 1996 | pp=405–423}} This leads the person to believe the dream is real, even when the dreams are absurd in nature.{{sfn| Holowchak | 1996 | pp=405–423}} In ''De Anima'' iii 3, Aristotle ascribes the ability to create, to store, and to recall images in the absence of perception to the faculty of imagination, ''phantasia''.{{sfn| Shields | 2016}}

One component of Aristotle's theory of dreams disagrees with previously held beliefs. He claimed that dreams are not foretelling and not sent by a divine being. Aristotle reasoned naturalistically that instances in which dreams do resemble future events are simply coincidences.{{sfn| Webb | 1990 | pages=174–184}} Aristotle claimed that a dream is first established by the fact that the person is asleep when they experience it. If a person had an image appear for a moment after waking up or if they see something in the dark it is not considered a dream because they were awake when it occurred. Secondly, any sensory experience that is perceived while a person is asleep does not qualify as part of a dream. For example, if, while a person is sleeping, a door shuts and in their dream they hear a door is shut, this sensory experience is not part of the dream. Lastly, the images of dreams must be a result of lasting impressions of waking sensory experiences.{{sfn| Modrak | 2009 | pp=169–181}}