Review of Is Marx’s Theory of Profit Right? The Simultaneist-Temporalist Debate


Is Marx’s Theory of Profit Right? The Simultaneist-Temporalist Debate, edited by Nick Potts and Andrew Kliman

Lexington Books, Lanham, MD, 2015. 194pp., $80.00 / £52.95 hb.  ISBN 9780739196311

Reviewed by Roel Van de Pol

This review was first published on the Marx and Philosophy Review of Books website on July 30, 2016.


For several decades now, proponents of the Temporal Single-System Interpretation (TSSI) have claimed that they have refuted an established “truth” that went essentially unchallenged for more than a century: the proof that Marx’s value theory, taken as he presented it, leads to logically inconsistent conclusions. The TSSI states, in short, that if Marx’s Capital is interpreted temporally (i.e. output unit values/prices are not considered equal to the unit values/prices of inputs needed to produce them) and in a single-system manner (i.e. the value transferred by inputs to outputs equals their prices, not their values), all of his disputed conclusions can be logically deduced from his presuppositions. By accepted exegetical standards, this would prove the superiority of TSSI authors’ reading of Marx. This claim directly contradicts the conventional interpretations of Marx, which TSSI proponents call simultaneist, that accept the proof of his inconsistency but claim to provide a viable correction to Marx’s supposed errors, contradicting some of his conclusions, but maintaining those that are (supposedly) essential to his world view.

Is Marx’s Theory of Profit Right provides a revealing insight into the way in which the debate between leading TSSI proponents and some of their principal critics has been conducted since the start of this century. Although the non-specialist will have to seriously refresh her or his math, the key issues and, perhaps even more essentially, the way in which proponents and critics have responded to each others arguments, are fairly accessible. The collection will most likely leave the reader quite impressed with the serious attitude of its TSSI-adherent editors, Nick Potts and Andrew Kliman, for republishing their opponents’ articles, allowing the reader to accurately form her or his own opinion. It is far from evident that they would have been granted the same courtesy. The introduction by Potts effectively summarizes the unscholarly methods with which critics have sought to suffocate the TSSI.

The issue that this collection focuses on is TSSI authors’ contention that “simultaneist” approaches confuse the coexistence of surplus labor and profit with the idea that surplus labor is a necessary and sufficient condition for profit. If we abide by the restrictive conditions adopted by simultaneist interpretations, profit does in fact always coexist with surplus labor. Proponents of these interpretations claimed that this coexistence proves that surplus labor is a necessary and sufficient condition for profit. However, as soon as the restrictions are loosened, this coexistence breaks down under certain circumstances. In particular, all simultaneist intepretations imply that profit can be negative even when surplus labor is positive. Hence, surplus labor is not a sufficient condition for profit. Whether the imposed restrictions are ever violated in the real world does not matter logically. Simultaneist approaches, therefore, cannot possibly be reconciled with Marx’s own value theory. Not even his essential conclusions, which the simultaneist approaches claim to rescue from inconsistency, survive this critique.

In their responses, Simon Mohun and Roberto Veneziani, critics of the TSSI, seem to be unable, or perhaps unwilling, to grasp the reasoning behind this argument. Instead of engaging in discussion to defend the claim that surplus labor is a necessary and sufficient condition for profit in simultaneist models, they initially launched a counterattack on the TSSI. Then, instead of challenging the logic behind the TSSI critique, they demanded mathematical proof that surplus labor and profit can ever fail to coexist in simultaneist models. Astonishingly, as soon as examples that satisfied this demand were provided by TSSI authors (Andrew Kliman and Alan Freeman), their critics made additional demands. They would accept that an example shows that surplus labor and profit can fail to coexist in simultaneist models only if the example is “economically meaningful” (45). The burden of proof was then raised two more times: the example had to be “empirically plausible” (64-65); finally it had to be “economically interesting” (111) as well. All this ignores the logic of necessary and sufficient conditions, which does not require any of these conditions to be met. Finally, Mohun and Veneziani ended up by completely ignoring the TSSI critiques and rejoinders.

Regardless of whether one upholds the TSSI or any other interpretation of Marx’s economic writings, the hostile attitude the TSSI authors were confronted with is quite striking. In that sense a separate discussion, in the second part of the collection, between philosopher Robert Paul Wolff and (mostly) Andrew Kliman, is quite a relief. Unfortunately, after a fairly healthy and honest debate, Wolff likewise seems to miss the point Kliman tries to make, causing him to unjustly regard Kliman’s insistence on settling the original debate as unwillingness to discuss Wolff’s alternative take on Marx.

For the non-specialist reader, Kliman’s Reclaiming Marx’s Capital (2007) most likely provides a more accessible insight into the essence of the debate, and the core differences between competing interpretations, than this new collection. However, Is Marx’s Theory of Profit Right serves two equally important purposes: not only does it allow the skeptical reader to verify with her or his own eyes the utter inability of the TSSI’s critics – thus far – to provide its proponents with an adequate response. It also stands as valuable evidence of the unscholarly and even unscientific methods of some, if not many, in the field of economics.

Personally, I stand by one of the closing remarks of Kliman and Freeman in their final article: the debate is over.


About the reviewer

Roel Van de Pol holds a MA degree in History from the Catholic University of Leuven and is a member of Comac, the student movement of the Workers’ Party of Belgium (


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