Page 43: “The use-value, coat, linen, &c., i.e., the bodies of commodities, are combinations of two elements–matter and labour. If we take away the useful labour expended upon them, a material substratum is always left, which is furnished by Nature without the help of man. The latter can work only as Nature does, that is by changing the form of matter. Nay more, in this work of changing the form he is constantly helped by natural forces. We see, then, that labour is not the only source of material wealth, of use-values produced by Labour. As William Petty puts it, labour is its father and the earth its mother.”
Labor, then, is useful and purposeful activity expended upon substances provided by nature in order to change their form. And, as we’ve seen from before, if we abstract from a commodity the particular material substance, and the exact form of the labor, what is left is human labor in the abstract.
The point is that, for now, we will refer for the sake of simplicity to labor, rather than doing the reduction of skilled labor to simple labor, as this will not change anything for this part of the investigation.
“So far as they are values, the coat and the linen are things of a like substance, objective expressions of essentially identical labour. But tailoring and weaving are, qualitatively, different kinds of labour. There are, however, states of society in which one and the same man does tailoring and weaving alternately, in which case these two forms of labour are mere modifications of the labour of the same individual, and no special and fixed functions of different persons.; just as the coat which our tailor makes one day, and the trousers which he makes another day, imply only a variation in the labour of one and the same individual. Moreover, we see at a glance that, in our capitalist society, a given portion of human labour is, in accordance with varying demand, at one time supplied in the form of tailoring, at another in form of weaving.”
Again, different kinds of labor, insofar as they are labor, can be equated as quantities; this is how commodities can be exchanged.
Page 44: Productive activity, if we leave out of sight its special form, viz., the useful character of the labour, is nothing but the expenditure of human labour-power.”
To get an idea of what Marx means by labor-power, it is useful to consider the difference between potential and kinetic energy. Labor-power is the ability to labor–when labor-power is expended, it becomes labor. So far, what we have read is little more than what has been discovered by earlier political economists (albeit expressed with exceptional clarity and precision); the important distinction between labor and labor-power constitutes one of the most important discoveries by Marx. In retrospect, of course, it is obvious: the ability to take an action is not the same as the action. But uncovering this distinction was as important to economics as changes in the form of energy was important to physics.
“The value of a commodity represents human labour in the abstract, the expenditure of human labour-power in general. And just as in society, a general or a banker plays a great part, but mere man, on the other hand, a very shabby part, so here with human labour. It is the expenditure of simpler labour-power, i.e., of the labour-power which, on an average, apart from any special development, exists in the organism of very ordinary individual. Simple average labour, it is true, varies in character in different countries and at different times, but in a particular society it is given. Skilled labour counts only as simple labour intensified, or rather, as multiplied simple labour, a given quantity of skilled labour being considered equal to a greater quantity of simple labour. Experience shows that this reduction is constantly being made. A commodity may be the product of the most skilled labour, but its value, by equating it to the produce of simple unskilled labour, represents a definite quantity of the latter labour alone.”
Here Marx inserts a footnote to remind the reader that, when we speak of skilled or simple labor, we are not speaking of the cost of that labor–ie, wages; which we’ll be getting to later.