Downing on Descartes and Extension

tags: Early Modern

Body & Extension

Downing’s discussion of Descartes’ position on interpenetration of matter perplexes me (or his position rather). Descartes seems to deny that there is ever any genuine interpenetration of one material body by another, only annihilation. But take two qualitatively identical bodies moving towards one another with equal force. What decides which one gets (partially) annihilated on impact? There doesn’t seem to be anything that would. That seems weird.

Summary of the Argument

What is Downing arguing for in this paper?

Downing’s aim is a bit diffuse. She states that

I focus here, however, on [Locke’s] attempts to prove in 2.13.11-14 that body and extension are distinct ideas. My goal is both to evaluate this anti-Cartesian foray, and to use it to reflect on some intriguing and abstruse elements of Descartes’ ontology of body. I’ll also use it to motivate some general reflections on Locke’s relation to Descartes. (1)

Let’s just look at the structure of the paper

2.13.11-14: Locke contra Descartes on body vs. space
- Why it’s evident that body & extension are different ideas
  - First, Extension includes no Solidity, nor resistance to the Motion of Body, as Body does. (II.13.12)
  - Secondly, The Parts of pure Space are inseparable one from the other (II.13.13)
  - Thirdly, The parts of pure Space, are immovable (II.13.14)
Descartes on impenetrability and extension
Locke contra Descartes on impenetrability
Objections (and Replies) to Locke’s Position
1. partes extra partes
2. varieties of seperability
3. Ontology of space and traditional metaphysical categories
Conclusion

Some Objections

Downing raises the worry that Descartes and Locke are just talking past each other, defining <body> in different ways. She attempts to defuse this worry by arguing that

Descartes holds that all bodies are impenetrable and extended, as Locke holds that all bodies are solid and extended. Furthermore, Locke equates solidity and impenetrability (4)

But isn’t the important issue concerning not whether Descartes and Locke both think that bodies are extended and impenetrable but rather what is essential to <body>? And here isn’t there complete disagreement? Doesn’t that disagreement suggest that there may just be different concepts in play – different nominal definitions – for which we can construct different sciences?

Second, Downing adduces a further bit of evidence in arguing that

they both distinguish this universal quality of body from hardness, which is something different, and dependent on our sense of touch

The relevant ‘universal quality’ is, I take it, solidity or impenetrability. And while it is true that Locke distinguishes solidity from hardness, it is not on the basis of one being dependent on our sense of touch and the other not. For he says

The idea of solidity we receive by our touch: and it arises from the resistance which we find in body to the entrance of any other body into the place it possesses, till it has left it. (II.iv.1)

Downing is either misreading the text here or just misinterpreting Locke’s point about hardness, which isn’t that it is related to touch, but rather (and more specifically) that hardness is relative to feelings of pain/pleasure.

being generally called hard by us, which will put us to pain sooner than change figure by the pressure of any part of our bodies; and that, on the contrary, soft, which changes the situation of its parts upon an easy and unpainful touch.
(II.iv.4)

So I think it isn’t so easy to answer the worry that they just end up differing on what Locke would consider to be the nominal definition of <body>.

What’s more, Downing needs to be able to answer these worries to support her claim that D & L are in ‘near perfect agreement’ about <body> and that their main dispute must concern the concept of space.

Impenetrability & Essence

In one objection Downing raises against Pasnau’s interpretation she argues that since impenetrability is supposed by Descartes to follow from the essence of body, and thus from extension, we cannot rescue D’s argument by appeal to God’s decree that matter not interact in specific ways. She likens this to explaining a body’s tendency to rectilinear motion, which is extrinsic to body, and a result of God’s decree (10). But one question this reply raises is whether impenetrability is a relational property (and thus extrinsic) or an intrinsic property of body. If it is derivable solely from the essence of body, it must be intrinsic to body. But if impenetrability is understood to be the quality of excluding other bodies, then isn’t that relational?

This is perhaps clearer with Locke, who defines solidity in terms of that which hinders the approach of one body to another but then remarks that in solidity as opposed to impenetrability the former

carries something more of positive in it than impenetrability; which is negative, and is perhaps more a consequence of solidity, than solidity itself. This, of all other, seems the idea most intimately connected with, and essential to body; so as nowhere else to be found or imagined, but only in matter. (II.iv.1)

Locke seems to be arguing that solidity is not just the disposition to exclude but also the primitive positive quality of body. Is this another worry that we might raise concerning the different manner in which Descartes and Locke conceive of solidity/impenetrability?