Concept
Extension (metaphysics)
Overview
In metaphysics, extension signifies both 'stretching out' (Latin: extensio) as well as later 'taking up space', and most recently, spreading one's internal mental cognition into the external world.
The history of thinking about extension can be traced back at least to Archytas' spear analogy for the infinity of space. How far can one's hand or spear stretch out until it reaches the edge of reality? "If I arrived at the outermost edge of the heaven, could I extend my hand or staff into what is outside or not? It would be paradoxical [given our normal assumptions about the nature of space] not to be able to extend it."
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
In the original texts
Passages from public-domain books where Extension (metaphysics) is discussed.
They rightly think that only solid extension can make an impression on our senses. It thus seems to us that extension is an attribute which constitutes part of the metaphysical form, but we are far from thinking that extension constitutes its essence. However, before Descartes, some of the ancients made the essence of matter consist in solid extension.
Julien Offray de La Mettrie, Man a Machine
names the idea; a chapter is titled for it; states what it is
It is true, the idea of extension joins itself so inseparably with all visible, and most tangible qualities, that it suffers us to SEE no one, or FEEL very few external objects, without taking in impressions of extension too. This readiness of extension to make itself be taken notice of so constantly with other ideas, has been the occasion, I guess, that some have made the whole essence of body to consist in…
John Locke, An Essay Concerning Humane Understanding, Volume 1
names the idea; states what it is; author linked in the graph; opens on it
The termination of these three dimensions is what we call figure. This figure is moveable, separable, and divisible. Mobility, and separability are the distinguishing properties of extended objects. And to cut short all disputes, the very idea of extension is copyed from nothing but an impression, and consequently must perfectly agree to it. To say the idea of extension agrees to any thing, is to say it is extended.
David Hume, A Treatise of Human Nature
names the idea; states what it is; opens on it
Leibniz has another argument of a logical nature, as those already referred to are of a physical: "Those who claim that extension is a substance, reverse the order of words as well as of thoughts. Besides extension there must be a subject which is extended; that is to say, something to which it belongs to be repeated or continued. For extension is nothing but a repetition or continued multiplication of that which is…
John Dewey, Leibniz's New Essays Concerning the Human Understanding
names the idea; states what it is; opens on it
The difference between objective and subjective extension is one of relation to a context solely. In the mind the various extents maintain no necessarily stubborn order relatively to each other, while in the physical world they bound each other stably, and, added together, make the great enveloping Unit which we believe in and call real Space. As 'outer,' they carry themselves adversely, so to speak, to one another…
William James, Essays in Radical Empiricism
names the idea; states what it is
Philosophers who discussed Extension (metaphysics)
Related ideas
- Gottfried Wilhelm Leibniz
- An Essay Concerning Human Understanding
- Isaac Newton
- John Locke
- Metaphysics
- Mind
- Matter
- Nature
- Archytas
- René Descartes
- David Chalmers
- Baruch Spinoza
- Thought
- Scholasticism
- God
- Andy Clark
- Cambridge University Press
Place in the tradition
Part of British philosophy.