On Generation and Corruption

Summary

On Generation and Corruption (Greek Peri Geneseos kai Phthoras; Joachim translates the title On Coming-to-be and Passing-away) is Aristotle's two-book inquiry into the most basic kinds of natural change below the moon. It asks what happens when a new substance comes into existence or an old one is destroyed, how that differs from a thing merely changing its qualities or its size, what contact, action and mixture are, and how the four simple bodies, earth, water, air and fire, turn into one another. It sits between the Physics, which treats motion in general, and the Meteorology and biological works, which treat compounds and living things. Book I begins with a survey of predecessors. Aristotle sets the monists, who reduce all change to alteration of one stuff, against the pluralists Empedocles, Anaxagoras, Leucippus and Democritus, who treat coming-to-be as the gathering and scattering of permanent elements. He reserves real praise for Democritus, who alone argued 'from the science of nature' rather than dialectically, and then refutes the atomists' indivisible bodies. Against them he argues that there is unqualified coming-to-be, the generation of a substance from what is not yet that substance, and that it can go on forever because one thing's passing-away is another's coming-to-be. He distinguishes alteration, in which a perceptible subject persists while its qualities change (a body now healthy, now ill), from generation, in which nothing perceptible persists. He explains growth as food, potentially flesh, being converted into the form of flesh. He then analyses contact, acting and being acted upon, rejects Empedocles' pores and the void, and defines mixture: when two bodies of balanced power act on each other, a genuinely new uniform stuff results, whereas a drop of wine in ten thousand gallons of water simply vanishes into the water. Book II turns to the elements. The primary tangible contraries are hot and cold, dry and moist; their four possible pairings give fire (hot and dry), air (hot and moist), water (cold and moist) and earth (cold and dry). Because each shares a quality with its neighbours, every element can become every other, most easily those that differ by one quality, so the elements change in a cycle. Every compound contains all four. Aristotle then names the causes of coming-to-be: matter, form, and an efficient cause, which neither Plato's Forms in the Phaedo nor mere matter supply. That cause is the sun's yearly motion along the inclined circle of the ecliptic, generating as it approaches and destroying as it withdraws. In the closing chapters he argues that because being is better than not-being, and perishable things cannot be eternal individually, the continual recurrence of generation is the nearest approach to eternity, and that only cyclical sequences, such as rain and cloud, are absolutely necessary.

Plot or Argument

• Monists, pluralists and the praise of Democritus (I.1-2)

  Aristotle sets out the rival views of earlier thinkers, faults Plato for treating only the generation of elements, credits Democritus with a method drawn from nature, and examines the argument for indivisible magnitudes before rejecting it.

• Can anything come to be without qualification? (I.3)

  Unqualified coming-to-be is the generation of a substance; it never runs out because the passing-away of one thing is the coming-to-be of another, matter being the cause of this ceaseless succession.

• Alteration distinguished from generation (I.4)

  If a perceptible subject persists and only its qualities change, the change is alteration; if nothing perceptible persists, as when seed becomes blood or water becomes air, a new substance has come to be.

• How living things grow (I.5)

  Growth is not mere addition. Every part of the growing thing increases in form, and food that is potentially flesh is converted into actual flesh; the same food nourishes inasmuch as it is potentially flesh and causes growth inasmuch as it is potentially so-much flesh.

• Contact, action and passion (I.6-9)

  Aristotle defines contact, argues that agent and patient must be alike in kind and contrary in quality, and rejects the pores of Empedocles and the void of Leucippus as explanations of how one body acts on another.

• What mixture is (I.10)

  True combination occurs when constituents of comparable power act on each other and both change into an intermediate uniform stuff; when one far exceeds the other, the lesser is simply absorbed.

• Four qualities, four bodies (II.1-5)

  Hot, cold, dry and moist are the primary tangible contraries; their pairings yield fire, air, water and earth, which are transformed into one another, with no single element prior to the rest.

• Against Empedocles; the composition of compounds (II.6-8)

  Empedocles cannot explain how unchanging elements are comparable or how flesh and bone arise from them; every compound body in the region of the centre contains all four simple bodies.

• The causes of coming-to-be and the inclined circle (II.9-10)

  Neither the Forms nor matter alone can cause generation; the efficient cause is the sun's motion on the ecliptic, whose approach and retreat generate and destroy and measure the life-spans of living kinds.

• Necessity and the cycle (II.11)

  Only what recurs cyclically comes to be of absolute necessity: seasons, rain and cloud return on themselves, while men and animals recur only in species, not as the same individuals.

Characters

• Democritus and Leucippus, atomists criticised

  Aristotle praises Democritus for arguing from nature but rejects the indivisible bodies and the void by which the atomists explained generation as rearrangement.

• Empedocles, pluralist criticised

  Proposer of four unchanging roots joined by Love and Strife and of pores through which bodies act; Aristotle argues his elements cannot be transformed or compared.

• Anaxagoras, pluralist criticised

  Held that the uniform stuffs such as flesh and bone are elementary; Aristotle says he misunderstood his own claim that coming-to-be is alteration.

• Plato (Timaeus and Phaedo), predecessor criticised

  Faulted for treating only the generation of elements in the Timaeus and for making the Forms the cause of generation in the Phaedo, which cannot explain why generation is intermittent.

Lessons

• Changing versus becoming something new

  Aristotle's key distinction is between alteration, where the same perceptible subject persists with new qualities, and generation, where one substance perishes and another arises. A sick body that recovers is the same body; water that becomes air is no longer water. The distinction asks students to say precisely what remains through a change, a habit useful in chemistry, biology and theology alike.

  • Which of these is alteration and which generation in Aristotle's terms: a green apple ripening, wood burning, ice melting?
  • What does Aristotle mean by saying that in generation 'nothing perceptible persists'?
  • Why might it matter, in thinking about a human life, whether a person who changes greatly remains the same person?

• Experience before system

  In I.2 Aristotle says that lack of experience narrows our view of the facts, and that those who live close to nature form better principles than those who dogmatize from a few observations. He uses this to prefer Democritus's physical arguments to the Platonists' geometrical ones, even while rejecting Democritus's conclusion. The passage is an ancient statement of the duty to look before theorizing.

  • Why does Aristotle praise Democritus even though he thinks Democritus is wrong?
  • What is the difference between a 'scientific' and a 'dialectical' method of inquiry in this passage?
  • Where in your own studies have you seen a theory built on too few observations?

• The drop of wine in the sea

  Aristotle's theory of mixture holds that a true compound arises only when ingredients of comparable power act on one another and both change into something new. If one is overwhelmingly greater, the lesser is simply converted into it, as a drop of wine disappears into ten thousand gallons of water. Students can compare this with modern distinctions between mixtures, solutions and compounds, and notice what questions survive the change of theory.

  • Why does Aristotle say a drop of wine does not 'combine' with a great quantity of water?
  • How does his idea of a uniform mixture differ from the atomists' picture of particles side by side?
  • Which of his questions about mixture does modern chemistry still have to answer, even if differently?

• The sun's inclined path as cause of birth and decay

  Aristotle argues that a single uniform motion would cause only one kind of effect; generation and destruction need a motion that approaches and retreats. The sun on the ecliptic does this, so things come to be as it nears and decay as it withdraws, and each kind of living thing has a life measured by a period. The argument links the seasons, agriculture and mortality in one causal picture.

  • Why does Aristotle think the daily rotation of the heavens alone could not cause both coming-to-be and passing-away?
  • What evidence from farming and the seasons does he use to support his theory?
  • How does his remark that every life is measured by a period compare with Psalm 90's numbering of our days?

• Perpetual generation as a likeness of eternity

  In II.10 Aristotle says nature strives after the better, and since perishable things cannot possess being forever, God completed the universe by making coming-to-be continuous, the closest approximation to eternal being. The cycle of the elements imitates the circular motion of the heavens. This is Aristotle's god, a first principle of an eternal cosmos, not the Creator of Genesis; Christian readers such as Aquinas used his physics while rejecting the eternity of the world on the ground of revelation.

  • What does Aristotle mean when he says perpetual coming-to-be is 'the closest approximation to eternal being'?
  • Why do men and animals not 'return upon themselves' in the cycle as rain and cloud do?
  • How does Aristotle's picture of an eternal cycle differ from the biblical account of a world with a beginning and an end?

Context

On Generation and Corruption answers the Presocratic debate over whether anything truly comes to be. Parmenides had denied that what is can arise from what is not; Empedocles, Anaxagoras and the atomists responded by making generation a rearrangement of permanent elements. Aristotle's reply uses his own distinctions of matter and form and of potentiality and actuality, worked out in the Physics, to defend real generation while keeping a persistent substratum. The four-element, four-quality theory set out in Book II, with its pairings of hot, cold, dry and moist, became the common physical framework of Greek, Arabic and Latin natural philosophy and underlay much of later medicine and alchemy.

Composition

The treatise is usually dated to the middle of Aristotle's career, around 350 BC, though no precise date can be fixed. It refers back to the Physics and to On the Heavens and is in turn presupposed by the Meteorology. The library's text is the Oxford translation by H. H. Joachim, published in 1922 with Joachim's commentary on the Greek text.

Reception

Ancient commentaries survive by Alexander of Aphrodisias (in fragments) and John Philoponus. Averroes commented on the work, and it was read in Latin in the medieval universities among the libri naturales; Thomas Aquinas began a commentary on it. Alchemists drew on the doctrine that the elements change into one another through their qualities. Robert Boyle's The Sceptical Chymist (1661) attacked the four-element theory, and Lavoisier's chemistry at the end of the eighteenth century replaced it with a new definition of the element. The work was chosen for the Great Books of the Western World (2nd ed., 1990), volume 7.

Comparisons

• Posterior Analytics and Physics

  The Physics supplies the tools this treatise depends on, the substratum, the contraries and the four causes; On Generation and Corruption applies them to the narrower question of substantial change and closes by citing the Physics on eternal motion.

• Meteorology

  Meteorology begins where Book II leaves off, using the hot, cold, dry and moist to explain winds, rain, comets and the formation of metals and uniform stuffs.

• Timaeus

  Plato builds the elements out of geometrical triangles; Aristotle explicitly criticises this, objecting that planes cannot compose bodies with qualities and that the Timaeus treats only the generation of elements.

• On the Nature of the Universe

  Lucretius gives the fullest surviving statement of the atomism Aristotle rejects, with generation as the combination and separation of indivisible particles moving in void.

• The Sceptical Chymist

  Boyle's sceptical chemist questions whether fire analysis really reveals four elements or three principles, attacking the Aristotelian theory set out in Book II and reviving a corpuscular view close to the atomists Aristotle criticised.

• Elements of Chemistry

  Lavoisier defines an element as a substance not yet decomposed by analysis and shows water to be a compound, overturning the four-element scheme, while still asking Aristotle's question about what persists through chemical change.

Quotes

Medical Lens

This is a work of physics, not medicine, but it supplies the theory of four primary qualities (hot, cold, dry, moist) that Greek and later Galenic physicians used to describe bodies, foods and drugs. Its account of growth explains nutrition as food that is potentially flesh being converted into actual flesh, and it repeatedly uses the physician and the art of healing as its model of an agent that acts without being acted upon. The treatise does not discuss the four humours themselves; any link to humoral pathology runs through later writers rather than through this text.

• Book I, ch. 5

  Growth explained as food, potentially flesh, being converted into the form of flesh; the same food nourishes and causes growth in different respects.

  Ancient Medicine
• Book I, ch. 7

  The art of healing produces health without being acted on by the patient, while food acts and is acted on; used to distinguish first agents from last ones.

  Physicians Doctors Ancient Medicine
• Book II, ch. 2-3

  Hot, cold, dry and moist set out as the primary tangible contraries and paired to form the four simple bodies, the qualitative scheme later used in Greek medical theory.

  Ancient Medicine

Creative Prompts

• Classroom

  Make a diagram of Aristotle's square of opposition for the elements: place fire, air, water and earth at the corners, label each with its two qualities, and mark which changes require one quality to change and which require two.

• Essay

  Using I.4 and a modern chemistry textbook, write an essay on what persists when wood burns. Explain Aristotle's distinction between alteration and generation and say how far the modern account preserves or abandons it.

• Dialogue

  Write a dialogue between Democritus and Aristotle about whether anything really comes into being, with each giving his strongest argument and conceding one point to the other.

• Classroom

  Collect three examples of things that come to be and pass away on a yearly cycle where you live. Explain each in Aristotle's terms of the sun's approach and retreat, then explain it in modern terms.

Further Reading

• Aristotle On Coming-to-be and Passing-away: A Revised Text with Introduction and Commentary, H. H. Joachim

  The Greek text and commentary (Oxford, 1922) by the translator of the library's version.

• Aristotle's De Generatione et Corruptione (Clarendon Aristotle Series), C. J. F. Williams

  Translation with philosophical notes.

• Physics, Aristotle

  Books I-II on matter, form and the causes presupposed here.

• The Sceptical Chymist, Robert Boyle

  The 1661 dialogue that challenged the four-element theory.