Julio:
> Marx's presented his work as a progression -- going from highly abstract
> determinations to concrete manifestations. The content of Marx's
> categories evolved as he progressed in his work. If you don't grasp this, > how can you grasp his critique of political economy?
This is correct, but is also a complete non sequitur in terms of your argument concerning productive labour.
If you want to argue that your conception of productive labour is compatible with Marx's, it won't do at all to indulge in a lot of airy generalities about Marx's method. You actually have to go through Marx's work, and pick out the passages you think support your argument. Furthermore, you have to pick out the passages that might contradict your argument, and try to square them with one another, see if one older analysis is superseded by a newer one, etc.
> Marx's "definitions" are necessarily provisional
This is utterly banal. Any "definition" in science is provisional.
> Can you see how Marx's notion of productive labor has to be seen as
> evolving or, at least, as conditional upon particular assumptions?
No, because you have provided zero evidence for this claim. You have just engaged in a murky disquisition about Marx's method, and actually a fairly accurate one in my opinion, but ultimately totally irrelevant to your contention as long as you don't *show* the passages where Marx's notion of productive labour evolves.
Finally, off topic, but maybe of interest to you:
> And left material for Engels to compile another book on capitalist
> circulation and a third book on the totality of capital as production and > circulation together.
Engels did a lot of mischief, because he didn't just compile Marx's manuscript (which was actually the oldest of all the manuscripts, the French edition of _Capital_ Vol. I being the most up to date), but really functioned as a sort of co-author. For more on this, see this article from Science and Society:
http://www.oekonomiekritik.de/303Engels%20Edition%20Engl.htm
"The book published by Engels in 1894 is not a mere edition of Marx's manuscript, but a far-reaching adaptation of the original manuscript. Only the smallest number of Engels' interventions is made visible. The largest extent of alterations remain obscured to the readers. The interventions themselves are not just of formal or stylistical nature, they deceive the readers about the actual extent of elaboration, they offer solutions for problems which the manuscript left open (without clarification that these are Engels' solutions!) and in some passages they even change the argumentation of the original text, if these obstruct Engels' interpretations. Therefore, Engels' edition can no longer be considered as volume III of Marx's Capital, it is not Marx's text "in the full genuineness of his own presentation", as Engels wrote in the supplement (Capital, Vol. III, p.889), but a strong editing of this presentation, a pre-interpreted textbook edtion of Marx's
manuscript.
The fact that Engels did not undertake a textual editing fulfilling modern demands is quite understandable from the point of view of those times. Editions did not have to fulfill such high demands concerning textual loyalty as is necessary today. An editor was given much larger freedom than today, especially if he was spiritually close to the edited author. Furthermore, it was most important to Engels to publish a book which could serve as an intellectual weapon for the working-class in the class struggle, which therefore was understandable and topical. And with all criticism we must not forget that it was an incredible achievement to publish this manuscript, of which Marx had once said in a letter to Engels that nobody at all could publish it in a readable form except for he himself (letter on February 13th, 1866).
Even still, all understanding for Engels' motives and procedure cannot at all alter the assessment that the text he has presented is by no means the third volume of Capital. Each future discussion of Marx's economic theory will have to refer to Marx's original manuscript."