Hertford to Hartford Lecture, 2006

Understanding the World, The Birth of Philosophy from Aristotle to The ancient Greeks, distinctively, Quantum Mechanics aimed for rational understanding independent of religious tradition. The Significance of Many different philosophers and “schools”: – Various “Pre-Socratics” (c. 600 - 400 BC) David Hume – Plato and his Academy (387 BC -) – Aristotle (pictured) and his Lyceum (335 BC -) Dr Peter Millican – Pyrrhonian sceptics (c. 320 BC -) – Epicureans (c. 307 BC -) Hertford College, Oxford – Stoics (c. 300 BC -) 2

Fixed Stars Saturn The Institution of Scholasticism Jupiter Mars Roman Empire became Christianised: Sun – Pagan temples and libraries destroyed 391 AD; Venus – Non-Christian “schools” closed down 529 AD. Mercury Moon Plato and Aristotle adopted: Fire – Christian Platonism (e.g. Augustine 354-430) Air – Christian Aristotelianism (e.g. Aquinas 1225-74) Water & Earth The Christian Aristotelian worldview became dominant in the medieval monastic schools, hence “Scholasticism”. Aristotle’s Universe 3 4

Rediscovery of the Classics Upheaval and Instability

Ancient texts survived in the Byzantine Many factors contributed to Western Empire, or in the Arabic world. instability in the period 1500-1650, e.g.: – Manuscripts brought West when the Ottoman – growth of population and trade; Turks attacked, fostered the development of – discovery of the New World (America etc.); Humanism in Renaissance Italy. Humanism in Renaissance Italy. – consequent economic disruption; Printing (invented 1450) gave them much – realisation that ancient maps etc. were wrong; wider circulation, e.g.: – suggestions of cultural relativity; – Lucretius (rediscovered 1417, printed 1486) – technology of gunpowder and consequent – Sextus Empiricus (translated into Latin 1562) centralisation of power.

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Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

The The Reformation Hereford “Mappa The Reformation added to this crisis: – Luther rebelled against the Church of Rome, Mundi” starting in 1517; (c. 1290) – Many parts of Europe (especially in the North) became Protestant; based on the writings – Savage wars throughout Europe arising from of Orosius, a pupil of religious differences (e.g. Thirty Years’ War Saint Augustine, part of a compendium of 1618-48, English Civil War 1639-51); knowledge to refute – Peace “of exhaustion” at Westphalia, 1648 led the pagans to greater religious toleration. 7 8

The Problem of the Criterion Aristotelian Science

A sceptical problem raised by Sextus Elements and Natural Motions Empiricus in his Outlines of Pyrrhonism: – Four elements: fire, air, water, and earth. How can any criterion of reliable knowledge – Fire/air naturally move upwards, water/earth be chosen, unless we already have some downwards, each seeking its natural place. reliable criterion for making that choice? A Teleological Physics – Roman Catholics appeal to tradition (Church, – Strivings, horror of a vacuum etc. Bible, Aristotle); Protestants appeal to the – Everything strives towards the eternal, hence believer’s personal response to the Bible; heavenly bodies move in circles, and must be – How to know who is right? (Maybe neither?!) made of a fifth element, aether.

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Intelligibility, or Empty “Explanation”? Galileo’s Experiments

“Why does water rise up a siphon pipe?” Aristotle couldn’t explain: “Because Nature abhors – the flight of a cannonball; a vacuum.” – a sledge sliding on flat ice; “Why does opium – water dripping from a gutter. make one sleep?” Galileo suggested (and claimed to have “Because opium has a Galileo suggested (and claimed to have dormitive virtue, whose carried out) another critical experiment: nature is to stupefy the – dropping a heavy and a light ball together from senses.” the Leaning Tower of Pisa. Molière (1673) 11 12

Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

Galileo’s Telescope Sun Venus as considered The telescope was invented in Holland in by Ptolemy 1608, and Galileo made his own in 1609. Venus What he saw with it refuted Aristotle’s cosmology: – Mountains and valleys on the moon; – Four moons orbiting around Jupiter; – Innumerable stars too dim for the naked eye;

– Phases of Venus, sometimes “full” (implying that Earth it is then on the opposite side of the Sun). 13 14

From Final to Efficient Causes The “Mechanical Philosophy”

Aristotelian science was based on The paradigm of efficient causation is via purposes, or “final” causation: mechanical contact: – Things strive to reach their natural place, or to – Interaction between contiguous particles of avoid abhorrent situations (e.g. a vacuum); matter by pressure and impact. Galileo preferred “efficient” causation: Compared with the pseudo-explanations – The outcome depends on where the causal involving “occult” qualities (horror of a sequence happens to lead. vacuum, dormitive virtue etc.), this seems: – Matter doesn’t strive; it is inert, remaining in – genuinely explanatory; its state of motion or rest unless acted on. – genuinely intelligible.

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The Father of Modern Philosophy Descartes and Essences

Attacks Aristotle The properties of matter follow from its using the sceptical essence, simple geometrical extension problem of the criterion; (i.e. extendedness in space). Builds on Galileo’s – Laws are mathematically expressible (e.g. in mechanical philosophy the framework of “Cartesian” co-ordinates). – Bodies are passive, remaining in the same grounding it on a theory state (inertia) until a force is applied. of matter’s “essence”; Mind is a distinct, active immaterial Makes room for mind Makes room for mind substance, whose essence is thinking. as a distinct “essence”. 17 18

Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

Descartes’ Physics The Monster of Malmesbury (and Magdalen Hall = Hertford College!) Since matter’s essence is extension, non- material extension is impossible. Thus: Hobbes denies – The physical world is a plenum (no vacuum); – immaterial substance; – All motion must take the form of circuits of – witchcraft; matter within the plenum. – reliance on revelation. – This can be expected to give rise to vortices, Hobbes asserts circular motions like whirlpools. – universal determinism; – A vortex can explain why the planets orbit the – obedience to sovereign Sun without shooting off under inertia. in religion and morals.

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Hobbes’ Materialism and Atheism Leviathan (1651) Hobbes sees “immaterial substance” as a contradiction in terms. In the state of – So everything that exists is material, even God nature, the life of and the angels. man is ‘solitary, Many took Hobbes to be an atheist. poore, nasty, Many took Hobbes to be an atheist. brutish and short’. – In 1666 Parliament cited his “atheism” as The only solution probable cause of the plague and fire of London! is absolute – His books were publicly burned in Oxford in sovereignty. 1683, because of their “damnable doctrines”. 21 22

The Evils of “Hobbism” Opposing Materialism

In 1668, Daniel Scargill of Corpus Christi The main argument against Hobbist Cambridge was expelled. In his public materialism was to insist on the limited powers recantation, he confessed: of “brute matter”, which: “I have lately vented and publickly asserted … – is necessarily passive or inert (as demonstrated by divers wicked, blasphemous, and Atheistical the phenomenon of inertia); positions … professing that I gloried to be an – in particular, cannot possibly give rise to mental Hobbist and an Atheist … Agreeably unto activity such as perception or thought. which principles I have lived in great This point was pressed by Ward (1656), More licentiousness, swearing rashly, drinking (1659), Stillingfleet (1662), Tenison (1670), intemperately … corrupting others …” Cudworth (1678), Glanvill (1682), Locke (1690).

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Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

Boyle’s Corpuscularianism Meanwhile, in the Heavens … Robert Boyle speculated that material substances are made In 1627 Johannes Kepler published tables of imperceptible “corpuscles”. enabling the calculation of planetary positions to an accuracy which turned out to be over – Corpuscles are both extended to an accuracy which turned out to be over and impenetrable. 1000 times better than any previous method. – Empty space is extended but Kepler’s method is based on the hypothesis penetrable. Hence extension is not identical with that each planet moves in an ellipse around matter, and a vacuum is a possibility. the Sun (which is at one “focus” of the ellipse). – The word “corpuscularianism” avoids the The method’s sheer accuracy led over time to atheistic associations of ancient “atomism”. general acceptance of that hypothesis. 25 26

Newtonian Physics Refuting Aristotle and Descartes

Isaac Newton took Newton’s theory could also predict – using Descartes’ concept of the very same equations – the motion of inertia, and Boyle’s theory cannonballs etc. on Earth. of “atoms and the void”, but – Another nail in the coffin of the Aristotelian postulated a force of gravity acting through it. supposition that heavenly bodies act differently. – If gravity acts in inverse proportion to the square In his Philosophiae Naturalis Principia of the distance between two objects, and bodies Mathematica (1687), Newton also proved accelerate in proportion to the total force acting mathematical results indicating that a vortex on them, then the elliptical motion of the planets could not possibly generate elliptical motion. around the Sun can be elegantly explained. – Descartes’ theory was thereby discredited. 27 28

Newton’s Methodological Gravitation and Intelligibility Instrumentalism Newtonian gravity acts at a distance with Newton’s public response to the objection: no intermediate mechanical connexion. “Hypotheses non fingo” – But this is deeply “unintelligible”. – “I feign no hypotheses”; there’s no obligation to – Descartes had objected to the idea of gravity invent speculations about how gravity operates as “occult”: one body would have to “know” (at least until more evidence comes to light where the other was to move towards it. giving a basis for more than mere hypothesis). – Many Newtonians took the operation of – If the gravitational equations (etc.) correctly gravity to be proof of divine action, a new describe the observed behaviour of objects, resource against Hobbist materialism. then that theory should be accepted whatever – Newton took a more instrumentalist attitude. the unperceived underlying reality might be. 29 30

Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

Overview: Intelligibility and Man is distinctively rational, made in the Why It Matters image of God to understand His universe. – Geometric physics gets closest to divine Reason. Aristotle’s world is intelligible because it is The intelligibility of matter reveals not only its completely driven by purposes – even powers, but equally importantly its limits: inanimate objects strive towards goals. – Thinking matter is impossible, so there must be However Galileo, Descartes, Hobbes etc. an immaterial substance, making the soul dismissed this as an illusion: potentially independent of the body. – Aristotle’s purposes just describe what objects But gravitation poses a problem: actually do – they don’t explain it at all. – It may show the need for a divine overseer … – Only mechanical interactions are genuinely – … or that matter has more powers than we can intelligible, enabling us to understand why “understand”: if gravitation, then why not thought? 31 things act as they do. 32

David Hume, 1711-76 Hume on Mechanical Causation

Newton is right to insist Suppose we see a yellow billiard ball that science can be done moving towards a red one and colliding with without intelligibility. it. Why do we expect the red one to move? Gravity is “unintelligible”, but mechanical causation is equally unintelligible. The aim of science is to describe things’ observed behaviour as simply as possible, in terms of the fewest possible causes.

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A Thought Experiment “Intelligibility” and Experience

Imagine Adam, newly created by God, The “intelligibility” of mechanical causation trying to envisage what would happen: seems to be an illusion, based on familiarity. – how could he possibly When we have repeated experience, our make any prediction at all expectation comes so naturally that we in advance of experience? imagine we could have known – even the first time – what would happen. That’s wrong: only experience can tell us what causes what. But are we justified in extrapolating this experience to the future?

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Peter Millican, Hertford College, Oxford Hertford to Hartford Lecture, 2006

Why Expect Uniformity? Hume on Induction – Negative

What ground can we give for expecting In advance of experience, we cannot know future events to resemble past events? anything about what causes what. – Self-evidence? No. – So experience is our only basis for making – Logical reasoning? No: neither of these, predictions about the unobserved. because it’s clear that extrapolation could fail, All inference from experience is based on so it can’t be a matter of pure logic. the assumption that we can extrapolate – Sensory knowledge? No: what we perceive from observed to unobserved (“induction”). of objects gives us no insight into the basis of – But this assumption has no rational their powers, hence no reason to extrapolate. foundation whatever! The basis of our reason – Experience? No: that would be circular. is animal instinct rather than angelic insight. 37 38

Hume on Induction – Positive Example: Miracles

The Foundation of Inductive Reasoning Why Do I Believe a Miracle Report? – Scientific (like all empirical) reasoning is – Because I have experience that reports of founded not on insight, but on a brute witnesses tend to be true. My belief is based assumption that the future will resemble the on inductive extrapolation. past, for which no solid basis can be given. Why Shouldn’t I Believe a Miracle Report? Good and Bad Reasoning – Typically, the inductive evidence against any – But this doesn’t mean that all inductive miracle will be far stronger than the inductive reasoning is equally good (or bad). The wise evidence in favour. I have lots of experience thing to do is to reason consistently with this of people being mistaken, misled, tricked … irresistible brute assumption. 39 40

Immanuel Kant (1783) Hume’s Triumph!

Hume has to be wrong, Einstein’s General Relativity (1915) because we have clear – Space is gravitationally “curved” examples of “synthetic a – So Euclid’s axioms probably aren’t true, and priori” knowledge: truths they’re certainly not knowable a priori. about the world knowable independently of Quantum Mechanics (1925) experience, that we see had to be that way: – Fundamental particles don’t work at all as we – Metaphysical principles (e.g. universal causation) (or Newton) would have expected: their – Euclidean geometry (e.g. Pythagoras’ theorem) behaviour is describable, but not “intelligible”. – Newtonian mechanics (e.g. conservation of – Genuine randomness seems to be ubiquitous. momentum). 41 42

Peter Millican, Hertford College, Oxford