As Marx said, every child knows that a social formation which did not reproduce the conditions of production at the same time as it produced would not last a year. 2 The ultimate condition of production is therefore the reproduction of the conditions of production. This may be 'simple' (reproducing exactly the previous conditions of production) or 'on an extended scale' (expanding them). Let us ignore this last distinction for the moment.
What, then, is the reproduction of the conditions of production?
Here we are entering a domain which is both very familiar (since Capital Volume Two) and uniquely ignored. The tenacious obviousness (ideological obviousness of an empiricist type) of the point of view of production alone or even of that of mere productive practice (itself abstract in relation to the process of production) are so integrated into our everyday 'consciousness' that it is extremely hard, not to say almost impossible, to raise oneself to the point of view of reproduction. Nevertheless, everything outside this point of view remains abstract (worse than one-sided: distorted) -- even at the level of production, and, a fortiori at that of mere practice.
Let us try and examine the matter methodically.
To simplify my exposition, and assuming that every social formation arises from a dominant mode of production, I can say that the process of production sets to work the existing productive forces in and under definite relations of production.