---
title: "Leviathan and the Air-Pump"
chunk: 3/9
source: "https://en.wikipedia.org/wiki/Leviathan_and_the_Air-Pump"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:36:51.494994+00:00"
instance: "kb-cron"
---

== Chapter III: Seeing Double: Hobbes's Politics of Plenism before 1660 ==
The third chapter centers on Hobbes' side of the debate for the effective production of knowledge.  However, unlike Boyle, Hobbes denies that natural philosophy can be separated from politics and religion.  In the previous chapter, Boyle's "matter of fact" worked towards separation from church and state by remaining objective and probabilistic.  For Hobbes, however, "the boundaries Boyle proposed to erect and maintain were guarantees of continued disorder, not remedies to philosophical dissension".  Hobbes also argued for "proper metaphysical language", in contrast to Boyle's reluctance to address the issue of a vacuum and his vague concept of air "pressure."  Hobbes was motivated by three things in his attack on Boyle: (1) to save his own reputation as a natural philosopher, (2) to develop a system of knowledge production that secured order and maintained proper goals for natural philosophy (namely precision instead of probability) and (3) to be sensitive to the needs of Restoration society (discussed in more detail in chapter 7).
Hobbes' denial of a vacuum stems in part from a need for political stability.  It follows logically that if there can be a space which is devoid of matter, then that is proof of "incorporeal substance" - an idea that was adopted by priests to gain the allegiance of the people by promising the safety of this substance, the immortal soul.  This splits the allegiance of each person in a country between the Church and the Monarch, which creates social instability and ultimately, for Hobbes, the risk of civil war.  He considered incorporeal substance a priestly conspiracy to "usurp power" from the true and legitimate leader - the King.  The conflict could be resolved "by collapsing the hierarchy [spiritual government and material government] in favour of matter".  "It was to that end that Leviathan proffered a materialist and monist natural philosophy.".
Leviathan also instructs that the way to produce good theories is through good definition of terms, the use of materialist and monist theory, and the equal importance of ontology and epistemology ("Show men what knowledge is and you will show them the grounds of assent and social order").  Hobbes works from a model of geometry, and the aims of his natural philosophy share the same precision as geometry.  That is why, for Hobbes, good definition is extremely important.  Hobbes also rejects the idea that the senses were reliable enough to be able to provide factual knowledge because "the same impressions could be obtained dreaming or waking, by the motions of matter in real external object or by rubbing the eyes".  Instead, Hobbes posits that man's own agency is the place for natural philosophy, once again drawing on geometry: "'as we know, that, if the figure shown be a circle, then any straight line through the centre shall divide it into two equal parts.'  'And this,' Hobbes said, 'is the knowledge required in a philosopher.'"  Thus, belief played no part in Hobbes' concept of a fact, and this ran in opposition to Boyle because Boyle's "matters of fact" required the consensus of a group of witnesses who all believed the same thing.  "Knowledge was constituted when all believed alike.  Likewise for Boyle's clerical allies, religion was a matter of belief and giving witness to that belief...[Hobbes] strategy was one of behavioural control, not one of internal moral control.  It was not that the control of belief was wrong; it was that such control was impractical and an inadequate surety for order."
Artfully, this chapter ends, "For Hobbes, the rejection of vacuum was the elimination of a space within which dissension could take place."

== Chapter IV: The Trouble with Experiment: Hobbes versus Boyle ==
As the chapter title suggests, this chapter focuses on how these two historical figures interacted.  It starts with a list of Hobbes' criticisms of Boyle:

- [Hobbes] was skeptical about the allegedly public and witnessed character of experimental performances, and, therefore, of the capacity to generate consensus, even within the experimental rules of the game.

- He regarded the experimental programme as otiose.  It was pointless to perform a systematic series of experiments, for if one could, in fact, discern causes from natural effects, then a single experiment should suffice.

- He denied the status of "philosophy" to the outcome of the experimental programme.  "Philosophy", for Hobbes, was the practice of demonstrating how effects followed from causes, or of inferring causes from effects.  The experimental programme failed to satisfy this definition.

- He systematically refused to credit experimentalists' claims that one could establish a procedural boundary between observing the positive regularities produced by experiment (facts) and identifying the physical cause that accounts for them (theories).

- He persistently treated experimentalists' "hypotheses" and "conjectures" as statements about real causes.

- He contended that, whatever hypothetical cause or state of nature Boyle adduced to explain his experimentally produced phenomena, an alternative and superior explanation could be proffered and was, in fact, already available.  In particular, Hobbes stipulated that Boyle's explanations invoked vacuism.  Hobbes's alternatives proceed from plenism.

- He asserted the inherently defeasible character of experimental systems and therefore the knowledge experimental practices produced.