Lecture 18 Boyle and Hobbes: on Air-Pumps and the Leviathan
© Darrin Durant 2004
Boyle and Hobbes: on Air-Pumps and the Leviathan
*** The Rise of Experimentalism ***
 Scholastic Aristotelian authority: self-evident experience & certainty
 Mathematicians acquired authority via claimed certainty
 Experience: proper interpretation required
 Mathematical proof and Experiment could produce counterintuitive knowledge
 Certainty of mathematical claims = conditional. Relation to
world?
 Claims were not self-evident
 Make knowledge the product of experiment specifically
designed for the purpose (counter-intuitive)
 Connections?: practical and useful knowledge, instruments
 Also: anatomy and physiology, chemistry and alchemy
 Modern experiment: laboratories, instruments, exclude variables not
being tested, replicable, trusted professionals
 But how was the experimental philosophy established?
*** Boyle v. Hobbes ***
Contesting the rights to mechanism & social order
Robert Boyle (1627-1691)
New Experiments Physico-Mechanical (1660)
The Sceptical Chymist (1661)
The Origins and Forms of Qualities (1661)
Founding member of the Royal Society of London
Thomas Hobbes (1588-1679)
Leviathan (1651)
Dialogus physicus de natura aeris (1661)
De corpore (1665)
The “dogmatic bear” (never admitted to Royal Society)
 What they agreed upon: Mechanism. Matter cannot move itself. God
can produce the same effect by a number of different causes. A vacuum
either does not exist or is improbable. Matter is particulate. Achieving
consensus on knowledge brings social order. Disputes must be carried
out with civility, between Gentleman.
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Lecture 18 Boyle and Hobbes: on Air-Pumps and the Leviathan
© Darrin Durant 2004
*** Boyle and the Air-Pump ***
 Experimental apparatus produce “matters of fact”
 What are “matters of fact”?
 ‘Hypotheses’ and ‘causes’ are less knowable
 Establishing matters of fact:
 Aggregation of individuals’ beliefs
 Convince yourself, then persuade others
 Multiply witnesses. Make “virtual witnesses”
 Manage dissent
 Debate matters of facts, not causes and hypotheses
 Open forums for witnessing
 Trust between Gentleman
 The Air-Pump (the Machina Boyleana) [Robert Hooke, 1635-1703]
 A receiver, a pumping apparatus (cylinder), various valves to
control air flow, a rack and pinion device, various seals
 Exhausts the air
 Operational definition of ‘vacuum’: a space devoid, not of
body, but of air
 The “void-in-the-void” experiment (1660)
 Torricelli (1608-1647): inverted mercury tube in a dish of
mercury = “torricellian space” at top = a void or not?
 ‘Content’ of Torricellian space of no concern to Boyle
 3-foot long tube, filled with mercury, inverted in dish of
mercury, placed in the air-pump
 Seal and pump. Falls to height of 29 inches. 1 inch above dish.
 ‘Notions’: pressure, weight and ‘spring’ of the air
 Expectations: no pressure = mercury descends
pressure = mercury ascends
 Why not all the way down?
 Boyle says “leakage”
 A void?: air-pump can’t decide, so question irrelevant
 The “two marble discs” experiment (1660)
 Cohesion between two flat surfaces: separation = void?
 Uppermost marble disc lifts bottom disc
 Attach weight to bottom disc and lower into receiver
 ‘Notions’: unequal pressure of air on uppermost stone
 Expectations: diminished air pressure= discs fall apart
 Failed trial. Why?
 Boyle says “leakage”: quantity of air allowed cohesion
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Lecture 18 Boyle and Hobbes: on Air-Pumps and the Leviathan
© Darrin Durant 2004
*** Hobbes and the Leviathan ***
 “Philosophy” = how to infer causes from effects, or how effects follow
from causes
 Philosophers discuss the causes of things
 Philosophy aims at certainty
 A legitimate hypothesis: conceivable, and once conceded, the
effects follow by necessity
 Examples of certain and causal knowledge
 Geometrical: geometrical figures are drawn and described by
ourselves
 Civic philosophy: we make the commonwealth ourselves
Certainty a function of convention: we know what we make
 In natural philosophy: causes sought from effects = uncertain
 On Boyle’s “void-in-the-void” experiment
 The “Spring of the air” = absurd
 Hobbes says: this presumes matter can move itself
(Boyle: corpuscles have an ‘inherent vibratory mode’)
 Leakage = pump always full of air = alternative explanation
 Contra Boyle: leakage destroys matters of fact
 Torricellian space: no void; circular movement in the plenum
 Experiment: you have a bottle, with a hole in the bottom
and water flowing out. Close the top. What happens?
 Where does the air go?
 Sufficiently impelled air = penetrating
 On Boyle’s “two marble discs” experiment
 Explained by Hobbes’ theory of hardness
 Imagine infinitely hard and infinitely smooth bodies
 Separation = infinite velocity of inrushing air =
impossible
 Finite hardness and finite smoothness causes separation
 Sufficient force causes flexing, allowing the air in
 Boyle neither a vacuist nor a plenist, but Hobbes a plenist
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Lecture 18 Boyle and Hobbes: on Air-Pumps and the Leviathan
© Darrin Durant 2004
*** Boyle on ‘Order’ ***
 Strength of air-pump?: shows there can be no decision between void
or not, thus such hypothetical questions out of the bounds of
experimental philosophy
 Boundary between knowledge of effects and knowledge of causes
 Agree on matters of fact (can know effects)
 Experiments provide secure knowledge of matters of fact
 Knowledge of causes only conjectural
 God can produce the same effect by a number of different causes
 Thus: talk about causes is less credible than talk about effects
 Differences regarding hypotheses managed by toleration and trust
 Experimental philosophy = an ‘antidote to enthusiasm (natural
events interpreted as divine omens)’ + a support for established
institutions (co-operative, public, universal knowledge
eliminates disputes and ensures social order)
 Distrusts absolute authority (the dogmatism of certainty)
 Moderate Anglican Reformism
 Anti-materialist, anti-sectarian, anti-magical
 Dualism of brute and mostly passive matter organized by
(provided motion by) either immaterial spirit or God’s design
+ Dualism of Church and State, in which Church directs State
*** Hobbes on ‘Order’ ***
 Absolute compulsion required
 One can only compel behaviour, not beliefs and opinions
 Leviathan mandates words and actions
 God can produce the same effect by a number of different causes
Thus: start with causes
 Experimentalism cannot command assent
 Fragmented authority = civil war
 e.g.: seeing double (matter and spirit)
 matters of fact separate from convention?
 Cannot have knowledge of God = Leviathan rules!
 All experiments have theory built into their design and construction
 Recall Harvey on the circulation of the blood
 Hobbes: not personal experience, but correct method,
that convinces us of circulation. Why?
 Always multiple causes compatible with an effect
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