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>Me: I apologize. I should have been more careful. The "long period"
>methodology can be employed in a "critical" manner or a "positive"
>manner. I think its critical employment is perfectly legitimate. Sraffa
>employed the long period method (more precisely: the static equilibrium
>method) critically, in an internal critique of neoclassical theory that
>had heretofore employed it in a positive manner. He showed that what the
>neoclassicists of his time had taken to be the necessary results of their
>theory were not in fact necessary results. Cool.
>It is only the employment of static equilibrium or "long period"
>methodology as an aspect of *positive* theory construction that I
>consider ridiculous -- more precisely, logically invalid. It attempts to
>deduce properties of the general case from the relations that happen to
>hold (tautologically) in the special case of static equilibrium. It is
>just not a logically valid move to pass from the special case to the
>general case in that way.
>Compare two static equilibria. First, any airplane A is in some airport
>X, on the ground. Sometime later, it is in some airport Y, also on the
>ground. "Ergo," airplanes cannot fly.
>The "Marxist" variant of this is: airplanes need to reproduce
>themselves. They do so by refueling. They refuel on the ground. Hence
>airplanes that reproduce themselves do so only on the ground. But we
>know that airplanes do reproduce themselves. "Ergo," airplanes cannot
>Notice that the method is logically invalid even when the equilibria are
>stable, as they are in the airplane case. Non-convergence to equilibria
>only compounds the basic problem.
>I have other complaints against static equilibrium methodology as well,
>but its logical invalidity is the chief one.
I do not understand the parallel you try to draw between the Sraffian
(simultaneous equation) model and the airplanes. The arguments you provide
to the conclusion that airplanes cannot fly are appallingly (obviously)
logically invalid. But that comment applies only to argument. The Sraffian
price system is an abstract model of prices in commodity production. The
model is not logically invalid. It says what it says, though there is a
question of the degree to which it corresponds to real world commodity
It would be logically invalid to conclude from the model that market prices
in actual market economies work (even with rents included) in the way the
model says. This is common in science. Galileo's model of motion on an
inclined plane assumes that there is no friction acting on the object
moving down the plane. It would be logically invalid to infer that objects
on real planes move as Galileo's model says they do, although they
sometimes do so approximately when the inclined plane and the object moving
down it are very smooth.
A Sraffian model does not assume that everything is bought and sold on the
same day. As I understand it, it assumes that the "most important
constraint" on (medium term) prices is the requirement that they pay for
replacement of what has been used up in production together with a normal
return on those replacement costs. How to cash out "important constraint"
is a matter of debate. You could use an "attractor" model or a boundary
model, with the constraint representing a condition that that separates
succesful from unsuccesful commodity producers over the long run, if
conditions remain the same.
As I understand your point (and I may well be missing it), it is that you
think that this idea is wrong and that we should be looking at capitalist
enterprises as essentially money making, where the return on outlays is
what is crucially important. If that is right, the case should be made in
that way without too much logical embellishment: after all, it is enough
that the Sraffian model picks out the wrong key feature to model (while
abstracting from all the rest). Saying it is "logically invalid" just says
you can't infer from a model to reality (which is the case even with good
models, or evenwith any of Allin's, which will not actually represent
relative prices at any time in a commodity producing economy)
Associate Professor Ian Hunt,
Director, Centre for Applied Philosophy,
Philosophy Dept, School of Humanities,
Flinders University of SA,
Bedford Park, SA, 5042,
Ph: (08) 8201 2054 Fax: (08) 8201 2784
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