[ Nancy Cartwright (1999), The Dappled World (Cambridge University Press), pp. 49-74. ]
1. Where do laws of nature come from?
2. An illustration from physics of a nomological machine
3. Models as blueprints for nomological machines
4. Capacities: openness and invention
5. Do we really need capacities?
6. Metaphysical aside: what makes capacity claims true?
7. Nomological machines and the limits of science
1. Where do laws of nature come from?
p.49 #1
The view of post-logical-positivist empiricists
: Laws of nature are basic and other things come from them.
Cartwright follow Rom Harre in rejecting this story.
Capacities are basic
and laws of nature obtain on account of the capacities;
or more explicitly, on account of the repeated operation of a system of component with stable capacities.
Sometimes the arrangement of the components and the setting
are appropriate for a law to occur naturally.
But in any case, it takes what Cartwright calls nomological machine to get a law of nature.
p.49 #2
p.50 #1
A nomological machine is a fixed (enough) arrangement of components or factors, with stable (enough) capacities that in the right sort of stable (enough) environment with, with repeated operation, give rise to the kind of regular behaviour that we represent in out scientific laws,
the role of nomological machines in generating a variety of different kinds of laws: the laws we test in physics, causal laws, results in economics and probabilistic laws
2. An illustration from physics of a nomological machine
p.50 #2
Kepler's law
: we have to establish the arrangement and capacities
of mechanical elements and the right shielding conditions
that keep the machine running properly
so that is gives rise to the Kepler regularities.
p.50 #3
Newton's achievement was to establish the magnitude of the force
required to keep a planet in an elliptical orbit.
The shielding condition is crucial here.
To ensure the elliptical orbit, the two bodies must interact
in the absence of any additional massive body and of any other factors
that can disturb the motion.
p.51 #1
Newton's solution to Kepler's problem
(1) Newton showed that the elliptical geometry of the orbit determines
the inverse-square kind of attraction.
(2) Conversely, he also showed that an attraction could give rise to
the observed regularity of the elliptical motion of Mars.
In both cases, the mechanical concept of force is assumption
that in the right circumstances a force has the capacity
to change the state of motion of massive body.
p.52 #1
Cartwright does not deny the unifying power of the principles of physics.
But she does deny that these principles can generally be reconstructed as regularity laws.
Newton's 'law of gravitation' is not a statement of a regular association between some occurrent properties, instead, about the force between them.
The term 'force' does not refer to yet another occurrent property like mass or distance.
Rather, it is an abstract term that describes the capacity of one body to move another towards it.
A capacity that can be used in different settings produces a variety of different kinds of motions.
p.52 #2
3. Models as blueprints for nomological machines
p.53 #1
On the physics side: chapter 4, chapter 8
On the economics side: chapter 6, chapter 7
p.53 #2
3. Models as blueprints for nomological machines
4. Capacities: openness and invention
5. Do we really need capacities?
6. Metaphysical aside: what makes capacity claims true?
7. Nomological machines and the limits of science
(2015.07.20.)
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