In a recent survey of the debate, a proponent of the TSSI concludes that "the proofs of inconsistency are no longer defended; the entire case against Marx has been reduced to the interpretive issue".
They claim that Marx's formulations fail to do this, but also what they characterize as his fundamental insights can be revealed, and extended, by means of models and concepts that emerged after his time.
Instead of trying to defend the consistency of Marx's original statements, non-TSSI Marxist theorists pursue what they characterize as ever-more effective versions of what they claim to be the core theory.
TSSI authors have also challenged the "Fundamental Marxian theorem", which supposedly showed that Marx's value theory is unnecessary in order to arrive at his conclusion that exploitation of workers is the unique source of profit under capitalism.
Proponents of the TSSI include, among others, Guglielmo Carchedi, John Ernst, Alan Freeman, Paolo Giussani, Andrew Kliman, Eduardo Maldonado-Filho, Ted McGlone, Nick Potts and Alejandro Ramos Martinez.
The words "temporal" and "single-system" in the title of the TSSI refer to the two key differences between it and the interpretation of Marx's value theory derived from Ladislaus von Bortkiewicz that at one time dominated academic Marxist economics.
In contrast, the TSSI is "temporal" or non-simultaneous, holding that prices (and values) of inputs and outputs in Marx's theory need not be (and generally are not) equal.
Duncan K. Foley, a prominent critic of the TSSI, stated that "I understand [Alan] Freeman and [Andrew] Kliman to be arguing that Okishio’s theorem as literally stated is wrong because it is possible for the money and labor rates of profit to fall under the circumstances specified in its hypotheses.
I accept their examples as establishing this possibility.”[4]In 1906-07, Ladislaus von Bortkiewicz claimed to prove that Marx's account of "the transformation of commodity values into prices of production" (i.e., prices that allow businesses to obtain an average rate of return on their capital investments) was internally inconsistent.
"[8]Similarly, Andrew Kliman distinguishes between internal consistency on the one hand, and truth or correctness on the other, at least nine different times.
That is all that Okishio, or Roemer, or Foley, or I, or anyone else has ever claimed!” [11] Duncan Foley claimed: “I understand Freeman and Kliman to be arguing that Okishio’s theorem as literally stated is wrong because it is possible for the money and labor rates of profit to fall under the circumstances specified in its hypotheses.