In other words, the use value of a commodity to a capitalist precisely is its exchange value. That makes sense, but the same is plainly not true of the consumer. No matter how much socially necessary labour time goes in to the production of a chocolate tea pot, its use value to an non chocolate teapot fan is unaffected.
I don't think its plausible to claim that "value and socially necessary labour time are the same thing". After all, socially necessary labour could be used to make a product that isn't turned in to a commodity. I'm sure you were talking about commodities in particular when you made that point but I think the non-commodity example illustrates that whilst socially necessary labour supervenes on exchange value, that doesn't mean that exchange value is reducible to socially necessary labour (just as hydrogen is necessary for water but that doesn't make water reducible to hydrogen).
It seems to me that most plausible things we can say about socially necessary labour are that (1) it sets a floor on the exchange value of any commodity sold for profit (everything above that floor being surplus value) and (2) that it is the only thing that can *increase* exchange value of any given commodity. It seems that demand and other variable also affects exchange value, independently of SNL. Marx seems to acknowledge that there are other relevant variables, as in his discussion of uncultivated land, sentimental items etc that affect price. I’m trying to piece together these various observations Marx makes, I feel I am clearly not interpreting correctly how they all join up.
“In other words, the use value of a commodity to a
capitalist precisely is its exchange value”.
No. A crofter in the Scottish Highlands before the onset of the Capitalist mode of production, might say “I need a table, I shall make one”. He or she is determining that he or she wants the use-value of a table. This is not a commodity. It’s a table. You, now, right here in the Epoch of the Capitalist mode of production might head down to the woodyard and buy a load of wood and make yourself a table as a hobby. That’s not a commodity either. It’s not intended as one, anyway. A serf might be asked to make a table for the lord of the manor. That is a use-value, but as it’s not going on the market, it isn’t a commodity. The capitalist, however, manufactures tables to sell. This is the production of use-values; use-values for others. If they did not possess use-value, who would buy them? Commodities are use-values.
Commodities are also exchange-values. Because they’re made for the market. They are desired because they are use-values, but they are commodities because they are also exchange-values. But what is that exchange-value a representation of? It’s a representation of socially necessary labour time.
Supply and demand plays a role in determining exchange-value, because the use-value decreases if I have several tables already and there’s nothing but tables on the market. I certainly desire tables a bit less at this point. But Marx points out in the section of fetishism of commodities (
Economic Manuscripts: Capital Vol. I - Chapter One ) that “in the midst of all the accidental and ever fluctuating exchange relations between the products, the labour time socially necessary for their production forcibly asserts itself like an over-riding law of Nature”.
“As a general rule, articles of utility become commodities, only because they are products of the labour of private individuals or groups of individuals who carry on their work independently of each other. The sum total of the labour of all these private individuals forms the aggregate labour of society. Since the producers do not come into social contact with each other until they exchange their products, the specific social character of each producer’s labour does not show itself except in the act of exchange. In other words, the labour of the individual asserts itself as a part of the labour of society, only by means of the relations which the act of exchange establishes directly between the products, and indirectly, through them, between the producers. To the latter, therefore, the relations connecting the labour of one individual with that of the rest appear, not as direct social relations between individuals at work, but as what they really are, material relations between persons and social relations between things. It is only by being exchanged that the products of labour acquire, as values, one uniform social status, distinct from their varied forms of existence as objects of utility. This division of a product into a useful thing and a value becomes practically important, only when exchange has acquired such an extension that useful articles are produced for the purpose of being exchanged, and their character as values has therefore to be taken into account, beforehand, during production. From this moment the labour of the individual producer acquires socially a two-fold character. On the one hand, it must, as a definite useful kind of labour, satisfy a definite social want, and thus hold its place as part and parcel of the collective labour of all, as a branch of a social division of labour that has sprung up spontaneously. On the other hand, it can satisfy the manifold wants of the individual producer himself, only in so far as the mutual exchangeability of all kinds of useful private labour is an established social fact, and therefore the private useful labour of each producer ranks on an equality with that of all others. The equalisation of the most different kinds of labour can be the result only of an abstraction from their inequalities, or of reducing them to their common denominator, viz. expenditure of human labour power or human labour in the abstract. The two-fold social character of the labour of the individual appears to him, when reflected in his brain, only under those forms which are impressed upon that labour in every-day practice by the exchange of products. In this way, the character that his own labour possesses of being socially useful takes the form of the condition, that the product must be not only useful, but useful for others, and the social character that his particular labour has of being the equal of all other particular kinds of labour, takes the form that all the physically different articles that are the products of labour, have one common quality, viz., that of having value.”
The process I think you are getting at of what a capitalist sees in a commodity, why they want to produce commodities, is discussed in this section.
Commodity fetishism is way that markets and money provide a disguise for what are actually social relations.
“Could commodities themselves speak, they would say: Our use value may be a thing that interests men. It is no part of us as objects. What, however, does belong to us as objects, is our value. Our natural intercourse as commodities proves it. In the eyes of each other we are nothing but exchange values. Now listen how those commodities speak through the mouth of the economist.
“Value” – (i.e., exchange value) “is a property of things, riches” – (i.e., use value) “of man. Value, in this sense, necessarily implies exchanges, riches do not.” “Riches” (use value) “are the attribute of men, value is the attribute of commodities. A man or a community is rich, a pearl or a diamond is valuable...” A pearl or a diamond is valuable as a pearl or a diamond.
So far no chemist has ever discovered exchange value either in a pearl or a diamond. The economic discoverers of this chemical element, who by-the-bye lay special claim to critical acumen, find however that the use value of objects belongs to them independently of their material properties, while their value, on the other hand, forms a part of them as objects. What confirms them in this view, is the peculiar circumstance that the use value of objects is realised without exchange, by means of a direct relation between the objects and man, while, on the other hand, their value is realised only by exchange, that is, by means of a social process.”
It's now become clear that I'm practically re-writing Capital in order to discuss just one sentence of yours.
So at this point I'm going to wind up.