| 16687 | Bodies are three-dimensional substances [Aquinas] |
| Full Idea: Bodies are those substances in which one finds three dimensions. | |
| From: Thomas Aquinas (Summa Theologicae [1265], Ia Q18.2c), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 16.2 | |
| A reaction: Pasnau points out that this extensional view of physical bodies was a commonplace long before Descartes. Presumably there are also non-dimensional substances (such as angels?). |
| 16684 | Impenetrability only belongs to the essence of extension [Descartes] |
| Full Idea: It is demonstrated that impenetrability belongs to the essence of extension and not to the essence of any other thing. | |
| From: René Descartes (Two letters on mind [1649], More, Apr 1649), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 15.5 | |
| A reaction: I'm not sure that I understand how pure extension can be impenetrable. |
| 16601 | Matter is not hard, heavy or coloured, but merely extended in space [Descartes] |
| Full Idea: The nature of matter, or body viewed as a whole, consists not in its being something which is hard, heavy, or colored, or which in any other way affects the senses, but only in its being a thing extended in length, breadth and depth. | |
| From: René Descartes (Principles of Philosophy [1646], 2.4), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 04.5 |
| 6518 | Matter can't just be Descartes's geometry, because a filler of the spaces is needed [Robinson,H on Descartes] |
| Full Idea: Notoriously, the Cartesian idea that matter is purely geometrical will not do, for it leaves no distinction between matter and empty volumes: a filler for these volumes is required. | |
| From: comment on René Descartes (works [1643]) by Howard Robinson - Perception IX.3 | |
| A reaction: Descartes thinks of matter as 'extension'. Descartes's error seems so obvious that it is a puzzle why he made it. He may have confused epistemology and ontology - all we can know of matter is its extension in space. |
| 13185 | Even if extension is impenetrable, this still offers no explanation for motion and its laws [Leibniz] |
| Full Idea: Even if we grant impenetrability is added to extension, nothing complete is brought about, nothing from which a reason for motion, and especially the laws of motion, can be given. | |
| From: Gottfried Leibniz (Letters to Burcher De Volder [1706], 1704 or 1705) | |
| A reaction: When it comes to the reasons for the so-called 'laws of nature', scientists give up, because they've only got mathematical descriptions, whereas the philosopher won't give up (even though, embarassingly, the evidence is running a bit thin). |
| 16683 | Leibniz eventually said resistance, rather than extension, was the essence of body [Leibniz, by Pasnau] |
| Full Idea: Leibniz eventually rejected extension altogether as part of the essence of body, and replaced it with resistance. | |
| From: report of Gottfried Leibniz (works [1690]) by Robert Pasnau - Metaphysical Themes 1274-1671 15.5 | |
| A reaction: This makes body consist of active force, rather than mere geometry. Much better. |
| 5615 | Extension and impenetrability together make the concept of matter [Kant] |
| Full Idea: Extension and impenetrability together constitute the concept of matter. | |
| From: Immanuel Kant (Critique of Pure Reason [1781], B646/A618) | |
| A reaction: Descartes had settled for extension alone. Kant's simple claim is probably now just a historical footnote, as we would now turn to physicists to define matter. Extension might survive, but impenetrability is not a key notion in quantum mechanics. |
| 6519 | Locke's solidity is not matter, because that is impenetrability and hardness combined [Robinson,H] |
| Full Idea: Notoriously, Locke's filler for Descartes's geometrical matter, solidity, will not do, for that quality collapses on examination into a composite of the dispositional-cum-relational propery of impenetrability, and the secondary quality of hardness. | |
| From: Howard Robinson (Perception [1994], IX.3) | |
| A reaction: I would have thought the problem was that 'matter is solidity' turns out on analysis to be a tautology. We have a handful of nearly synonymous words for matter and our experiences of it, but they boil down to some 'given' thing for which we lack words. |