# Re: [OPE-L] naive question on Sraffian model

From: Ian Wright (iwright@GMAIL.COM)
Date: Fri Dec 03 2004 - 12:50:28 EST

```Hi Ajit,

> There is no time and no causation in Sraffa's original
> work. Sraffa does not have a "model". His propositions
> are mathematical or logical in nature. What all
> different variants of Sraffians have done with it, is
> a different story altogether. Cheers, ajit sinha

But you have previously explained to me that the Sraffian model is a
theory of prices because it demonstrates that they are determined by
(i) technical coefficients, (ii) distributional variable, (iii)
uniform profit assumption. It does not explain prices by reference to
previous prices. But if there is no causality or order to this
explanation
then we could equally say that the Sraffian model is a theory of
distribution given (i) technical coefficients, (ii) uniform profit
assumption, (iii) relative prices. Isn't this a general problem with
acausal, simultaneous models? Essentially they define a function that
map inputs to outputs. Given a collection of inputs you get some
outputs, and hence the outputs are explained by the inputs. But you
can invert the function and get the inputs given the outputs. So which
comes first: the distributional variable or prices? Would you agree
that all presentations of the Sraffian framework smuggle in the
assumption that the order of explanation is such that it is prices
that are explained, rather than going the other way, and thinking that
it is prices that are taken as given? If we want to stick to the
intepretation that Sraffa's "model" is acausal then we cannot say it
"explains prices"; rather it determines a functional relation between
distribution and prices, given the assumptions. Just musing as this
critique will depend on the invertability of the function.

-Ian.
```

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