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27. Natural Reality / A. Classical Physics / 1. Mechanics / c. Forces

[attractions and repulsions in physical nature]

25 ideas
The ocean changes in volume in proportion to the attraction of the moon [Seneca]
     Full Idea: The waves increase by degrees, approaching to the hour and day proportionately larger or smaller in volume as they are attracted by the star we call the moon, whose power controls the ocean's surge.
     From: Seneca the Younger (On Providence [c.60], §1)
     A reaction: ....just in case anyone thought that Isaac Newton had invented gravity.
'Force' is the quantity of movement imposed on something [Hobbes]
     Full Idea: I define 'force' to be the impetus or quickness of motion multiplied either into itself, or into the magnitude of the movent, by means of which whereof the said movent works more or less upon the body that resists it.
     From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 3.15.02)
     A reaction: Not very helpful, perhaps, but it shows a view of force at quite an early date, well before Newton.
Newton's idea of force acting over a long distance was very strange [Heisenberg on Newton]
     Full Idea: Newton introduced a very new and strange hypothesis by assuming a force that acted over a long distance.
     From: comment on Isaac Newton (Principia Mathematica [1687]) by Werner Heisenberg - Physics and Philosophy 06
     A reaction: Why would a force that acted over a short distance be any less mysterious?
Newton introduced forces other than by contact [Newton, by Papineau]
     Full Idea: Newton allowed forces other than impact. All the earlier proponents of 'mechanical philosophy' took it as given that all physical action is by contact. ...He thought of 'impressed force' - disembodied entities acting from outside a body.
     From: report of Isaac Newton (Principia Mathematica [1687]) by David Papineau - Thinking about Consciousness App 3
     A reaction: This is 'action at a distance', which was as bewildering then as quantum theory is now. Newton had a divinity to impose laws of nature from the outside. In some ways we have moved back to the old view, with the actions of bosons and fields.
Newton's laws cover the effects of forces, but not their causes [Newton, by Papineau]
     Full Idea: Newton has a general law about the effects of his forces, ...but there is no corresponding general principle about the causes of such forces.
     From: report of Isaac Newton (Principia Mathematica [1687]) by David Papineau - Thinking about Consciousness App 3
     A reaction: I'm not sure that Einstein gives a cause of gravity either. This seems to be part of the scientific 'instrumentalist' view of nature, which is incredibly useful but very superficial.
Newton's forces were accused of being the scholastics' real qualities [Pasnau on Newton]
     Full Idea: Newton's reliance on the notion of force was widely criticised as marking in effect a return to real qualities.
     From: comment on Isaac Newton (Principia Mathematica [1687]) by Robert Pasnau - Metaphysical Themes 1274-1671 19.7
     A reaction: The objection is to forces that are separate from the bodies they act on. This is one of the reasons why modern metaphysics needs the concept of an intrinsic disposition or power, placing the forces in the stuff.
I am studying the quantities and mathematics of forces, not their species or qualities [Newton]
     Full Idea: I consider in this treatise not the species of forces and their physical qualities, but their quantities and mathematical proportions.
     From: Isaac Newton (Principia Mathematica [1687], 1.1.11 Sch)
     A reaction: Note that Newton is not denying that one might contemplate the species and qualities of forces, as I think Leibniz tried to do, thought he didn't cast any detailed light on them. It is the gap between science and metaphysics.
The aim is to discover forces from motions, and use forces to demonstrate other phenomena [Newton]
     Full Idea: The basic problem of philosophy seems to be to discover the forces of nature from the phenomena of motions and then to demonstrate the other phenomena from these forces.
     From: Isaac Newton (Principia Mathematica [1687], Pref 1st ed), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 4
     A reaction: This fits in with the description-of-regularity approach to laws which Newton had acquired from Galileo, rather than the essentialist attitude to forces of Leibniz, though Newton has smatterings of essentialism.
Boyle and Locke suspect forces of being occult [Locke, by Alexander,P]
     Full Idea: I believe that both Boyle and Locke were suspicious of forces, regarding them as occult.
     From: report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694]) by Peter Alexander - Ideas, Qualities and Corpuscles 7
     A reaction: I take this to be key difference between these two and Leibniz, with the latter on the side of the angels.
An insurmountable force in a body keeps our hands apart when we handle it [Locke]
     Full Idea: The bodies which we daily handle make us perceive that they do by an insurmountable force hinder the approach of the parts of our hands that press them.
     From: John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.04.01)
     A reaction: This is interesting for a rare use of the word 'force' by Locke. I like the empiricist approach to these things, of actually contemplating handling physical objects. Empiricism keeps the feet of philosophy firmly on the ground.
Some people return to scholastic mysterious qualities, disguising them as 'forces' [Leibniz]
     Full Idea: It pleases others to return to occult qualities or scholastic faculties, but since these crude philosophers and physicians see that those terms are in bad repute they change their name, calling them 'forces'.
     From: Gottfried Leibniz (Against Barbaric physics [1716], A&G:313), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 19.7
     A reaction: Deceptive, because Leibniz embraced forces in his revised Aristotelian essentialism. Leibniz placed forces within essences, and he is worried about forces as separate entities, unsupported by any substance.
Power is passive force, which is mass, and active force, which is entelechy or form [Leibniz]
     Full Idea: The dynamicon or power [potentia] in bodies is twofold, passive and active. Passive force [vis] constitutes matter or mass [massa], and active force constitutes entelechy or form.
     From: Gottfried Leibniz (On Body and Force, Against the Cartesians [1702], p.252)
     A reaction: This is explicitly equating the innate force understood in physics with Aristotelian form. The passive force is to explain the resistance of bodies. I like the equation of force with power. He says the entelechy is 'analogous' to a soul.
All qualities of bodies reduce to forces [Leibniz]
     Full Idea: All qualities of bodies .....are in the end reduced [revoco] to forces.
     From: Gottfried Leibniz (On Body and Force, Against the Cartesians [1702], p.256)
     A reaction: The dots conceal a long qualification, but he is essentially standing by this simple remark. If you substitute the word 'powers' for 'forces', I think that is just about right.
It is plausible to think substances contain the same immanent force seen in our free will [Leibniz]
     Full Idea: If we attribute an inherent force to our mind, a force acting immanently, then nothing forbids us to suppose that the same force would be found in other souls or forms, or, if you prefer, in the nature of substances.
     From: Gottfried Leibniz (On Nature Itself (De Ipsa Natura) [1698], §10)
     A reaction: This is the kind of bizarre idea that you are driven to, once you start thinking that God must have a will outside nature, and then that we have the same thing. Why shouldn't such a thing pop up all over the place? Only Leibniz spots the slippery slope.
We need the metaphysical notion of force to explain mechanics, and not just extended mass [Leibniz]
     Full Idea: Considering 'extended mass' alone was not sufficient to explain the principles of mechanics and the laws of nature, but it is necessary to make use of the notion of 'force', which is very intelligible, despite belonging in the domain of metaphysics.
     From: Gottfried Leibniz (New system of communication of substances [1695], p.139)
     A reaction: We may find it surprising that force is a metaphysical concept, but that is worth pondering. It is a mysterious notion within physics. Notice the emphasis on what explains, and what is intelligible. He sees Descartes's system as too passive.
Motion alone is relative, but force is real, and establishes its subject [Leibniz]
     Full Idea: Motion in itself separated from force is merely relative, and one cannot establish its subject. But force is something real and absolute.
     From: Gottfried Leibniz (Letters to Antoine Arnauld [1686], 1688.01.4/14)
     A reaction: The striking phrase here is that force enables us to 'establish its subject'. That is, force is at the heart of reality, and hence, through causal relations, individuates objects. That's how I read it.
The force behind motion is like a soul, with its own laws of continual change [Leibniz]
     Full Idea: I recognise, in the active force which exerts itself through motion, the primitive entelechy or in a word, something analogous to the soul, whose nature consists in a certain perpetual law of the same series of changes through which it runs unhindered.
     From: Gottfried Leibniz (Letters to Burcher De Volder [1706], 1699), quoted by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 6.1.3
     A reaction: This is a hugely metaphysical account of force, contrasting with Newton's largely mathematical account. He very often says that force is 'analogous' to the soul, rather than that it actually is a soul. He never quite believes that monads are real minds.
Force in substance makes state follow state, and ensures the very existence of substance [Leibniz]
     Full Idea: By the force I give to substances, I understand a state from which another state follows, if nothing prevents it. ...I dare say that without force, there would be no substance.
     From: Gottfried Leibniz (Letters to Lelong [1712], 1712), quoted by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 7.1
     A reaction: [the whole quote is interesting] This remark, more than any other I have found, places force at the centre of Leibniz's metaphysics. He is using it to resist Spinoza's one-substance view.
Clearly, force is that from which action follows, when unimpeded [Leibniz]
     Full Idea: The notion of force is as clear as that of action and passion, because it is that from which action follows when nothing prevents it.
     From: Gottfried Leibniz (Letters to Paul Pellison-Fontinier [1691], A1.6.226), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 4
     A reaction: For Leibniz, force seems to be a metaphysical notion, rather than a feature of the physical world. I take it to be the bottom level of explanation, and it equates with Aristotelian form and essence.
Leibniz uses 'force' to mean both activity and potential [Leibniz]
     Full Idea: At this early period exegetical problems abound, since Leibniz uses 'force' both for actually acting forces and for potentials or powers.
     From: Gottfried Leibniz (works [1690], 9.II), quoted by Harré,R./Madden,E.H. - Causal Powers 9.II.B
     A reaction: I take Leibniz to be a key figure in the development of the Aristotelian approach, because he connected Aristotelian potential and essence with 'force' in the new physics. This is helpful in reading him correctly.
Force is supposed to cause acceleration, but acceleration is a mathematical fiction [Russell]
     Full Idea: A force is the supposed cause of acceleration, ...but an acceleration is a mere mathematical fiction, a number, not a physical fact.
     From: Bertrand Russell (The Principles of Mathematics [1903], §448)
     A reaction: This rests on his at-at theory of motion, in Idea 14168. I'm not sure that if I fell off a cliff I could be reassured on the way down that my acceleration was just a mathematical fiction.
I deny forces as entities that intervene in causation, but are not themselves causal [Ellis]
     Full Idea: The classical conception of force is an entity that intervenes between a physical cause and its effect, but is not itself a physical cause. I see no reason to believe in forces of this kind.
     From: Brian Ellis (The Metaphysics of Scientific Realism [2009], 2)
     A reaction: The difference of view between Leibniz and Newton is very illuminating on this one (coming this way soon!). Can you either have forces and drop causation, or have causation and drop forces?
By 'force' I mean the sources of all actions - sometimes called 'powers' by their outcomes [Breheny]
     Full Idea: I mean by the word 'force' the source or sources of all possible actions of the particles or materials of the universe: these being often called the powers of nature when spoken of in relation to the different manners in which their effects are shown.
     From: Richard Breheny (Letter to Clerk Maxwell [1855]), quoted by Harré,R./Madden,E.H. - Causal Powers 9.II.B
     A reaction: He uses 'force' for what is fundamental, and 'powers' for their results. I am inclining to talk of 'fundamental powers' and 'complex powers', leaving the word 'force' to the physicists.
The strong force has a considerably greater range than the weak force [Martin,BR]
     Full Idea: The strong nuclear force has a range of 10^-15 m, considerably larger than the range of the weak force.
     From: Brian R. Martin (Particle Physics [2011], 01)
     A reaction: This is because the bosons transmitting the weak force (W+, W-, W°) are much heavier than the gluons of the strong force.
Relativity and Quantum theory give very different accounts of forces [Hesketh]
     Full Idea: General Relativity and quantum mechanics are the two great theories in physics today but they give two very different ideas for how forces work.
     From: Gavin Hesketh (The Particle Zoo [2016], 01)
     A reaction: Relativity says it is space curvature, and quantum theory says it is particle exchange? But is there a Relativity account of the strong nuclear force?