Materialism & Mechanism

Mechanism & Materialism

The seventeenth century saw the rise of two distinct but related positions: mechanism and materialism. Materialism is a metaphysical theory concerning the natural world. It claims that the natural world consists fundamentally of a kind of thing or stuff—matter—and that this stuff, organized in various ways according to natural laws as characterized by physics, determines the nature and features of all the objects we experience as part of the objective (and thus mind-independent) natural world. Materialism says that there is fundamentally only one kind of thing—matter. Materialism thus stands in opposition to a dualist view like that articulated by Descartes. Descartes argues that there are fundamentally two kinds of thing—matter, and mind—and that the natural world consists of these two kinds of thing interacting with one another, sometimes in very special ways (as with the ensouled bodies of human beings).

Mechanism is part of a theory of explanation. Lisa Downing, a scholar of the Early Modern period, puts it this way,

[Mechanistic doctrine] states that all macroscopic bodily phenomena should be explained in terms of the motions and impacts of submicroscopic particles, or corpuscles, each of which can be fully characterized in terms of a strictly limited range of (primary) properties: size, shape, motion (or mobility), and, perhaps, solidity or impenetrability. ((Downing 1998), 381)

A ‘corpuscle’ is a extremely small parcel of matter with a determinate size, shape, motion, location, etc. It is the features of individual corpuscles, plus their interactions, which mechanism takes as sufficient for explaining the characteristics and behavior of the natural (material) world. Thus, while the claim that the natural world consists of nothing but corpuscles, or material particles, is a metaphysical claim about what there is, mechanism is an explanatory claim concerning how appeal to microscopic particles and their features is sufficient for explaining all natural phenomena. These views thus compliment one another and often go together. But one needn’t be a materialist to endorse mechanism. For example, Descartes clearly endorses a mechanist outlook on material nature.

I considered in general all the clear and distinct notions which our understanding can contain with regard to material things. And I found no others except for the notions we have of shapes, sizes and motions, and the rules in accordance with which these three things can be modified by each other—rules which are the principles of geometry and mechanics. And I judged as a result that all the knowledge which men have of the natural world must necessarily be derived from these notions. (Principles 4:203; (Descartes 1985))

One of the primary attractions of mechanistic explanation is that they seem especially intelligible, given the assumption that material beings are understood primarily as having properties that admit entirely of mathematical/geometric analysis and explanation.

In contrast to Descartes, who aimed primarily at a conception of material nature that could in principle be entirely concieved through the basic or primary attribute of extension, Robert Boyle and John Locke (both English philosophers) endorsed a mechanism largely as a working explanatory hypothesis, that could be confirmed or refuted on empirical grounds.

As Boyle put it,

These Principles, Matter, Motion (to which Rest is related) Bigness, Shape, Posture, Order, Texture being so simple, clear, and comprehensive, are applicable to all the real Phaenomena of Nature, which seem not to be explicable by any other not consistent with ours. For, if recourse be had to an Immaterial Principle or Agent, it may be such an one, as is not intelligible; and however it will not enable us to explain the Phaenomena, because its way of working upon things Material would probably be more difficult to be Physically made out, than a Mechanical account of the Phaenomena. And, notwithstanding the Immateriality of a created Agent, we cannot conceive, how it should produce changes in a Body, without the help of Mechanical Principles, especially Local Motion ((Boyle 1991), 153-4).

For Boyle, mechanism is simply the most explanatorily simple, clear, and comprehensive theory we have regarding the material world, whether or not we think material nature is all that there is (i.e. whether or not we endorse materialism).

Locke himself also frames his understanding of mechanism in terms of what he calls the ‘corpuscularian hypothesis’.

I have here instanced in the corpuscularian hypothesis, as that which is thought to go furthest in an intelligible explication of those qualities of bodies; and I fear the weakness of human understanding is scarce able to substitute another, which will afford us a fuller and clearer discovery of the necessary connexion and coexistence of the powers which are to be observed united in several sorts of [bodies]. (ECHU IV.iii.16; (Locke 1970))

There is a great deal to be said about both the doctrine of materialism and that of mechanism, as well as their development and influence in the seventeenth and eighteenth centuries. But here I focus on just one issue—the specific properties corpuscles were thought to have, and the explanatory role of these properties relative to all the other apparent characteristics of objects.

Notice two things about mechanism. First, it ultimately concerns unobservable, or at least, unobserved entities (corpuscles). This means that the explanation of observable phenomena depends on the existence and characteristics of unobserved phenomena. This, in and of itself, is a dramatically anti-Aristotelian move. The fundamental explanatory level of reality is one which is removed, and perhaps ineluctably so, from our direct apprehension in experience.

Second, the explanatorily relevant features of corpuscles are taken by mechanists to be their geometric properties—viz., size, shape, location, and state of motion. What are not included are those features which we might think of as tied to specific ways of sensing the world—e.g. their colors, tastes, or smells.1 This bifurcation in explanatory role meant both that greater emphasis was placed on our mathematical understanding of the natural world, and that our purely sensory grasp of the natural world no longer played a significant role (perhaps no role at all) in telling us how and why the world appears to us as it does. To see this this shift to the characteristically modern version of the “primary/secondary” quality distinction at work, it helps to start with Galileo.


Boyle, Robert. 1991. Selected Philosophical Papers of Robert Boyle. Indianapolis: Hackett Publishing.

Descartes, René. 1985. “Principles of Philosophy.” In 1, edited by John Cottingham, Robert Stoothoff, and Dugald Murdoch, 177–291. Cambridge: Cambridge University Press.

Downing, Lisa. 1998. “The Status of Mechanism in Locke’s Essay.” The Philosophical Review 107 (3):381–414.

Locke, John. 1970. An Essay Concerning Human Understanding. Oxford: Oxford University Press.

  1. One feature—solidity—may or may not occupy a special role, being the only proper sensible (sensory quality tied to a specific sense modality, in this case touch) that may yet be explanatorily fundamental for the mechanist. ↩︎

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