In ope-l 3878, Allin wrote, in response to my ope-l 3876,
"Perhaps Andrew could explain what bearing he reckons the
quotation about rent has on the questions he poses after it.
I don't see any relationship myself."
Certainly. The key is Marx's phrase (my caps):
"IT IS NOT TRUE CONVERSELY THAT ANY SURPLUS PRODUCT IN THE SENSE OF A MERE
INCREASE IN
THE QUANTITY OF THE PRODUCT REPRESENTS A SURPLUS-VALUE."
It find it difficult to imagine how it might be possible that a surplus
product ("in the sense of a mere increase in the quantity of the product")
would not represent a surplus-value, if input prices (of production) must
equal output prices (of production), or if the values of inputs must equal the
values of outputs. If we imagine a vector of inputs (including means of
subsistence for workers), K, and a vector of outputs, X, then a surplus
product in the above sense exists if some elements of X - K are positive and
none are negative. Valuing X and K according to some vector p, which might
be unit prices or unit values, surplus-value is p(X - K). If all elements of
p are positive and a surplus product exists, then surplus-value must be
positive.
If, however, K is valued according to vector p(t) and X according to vector
p(t+1), then surplus-value is p(t+1)X - p(t)K. Even if a surplus product in
the above sense exists, if the elements of p(t+1) are "on average" small
enough relative to the elements of p(t), surplus-value can be negative.
Andrew Kliman