In the theory of the value-form, Marx sets out to unravel the riddle of a commodity’s price (i.e., the riddle of the money-form), while at the same time untangling the riddle of money. The riddle of the money-form concerns the fact that the value of a commodity is generally expressed in the form of a certain quantity of a particular use-value: gold. The riddle of money concerns how, in that case, gold’s use-value — which is the element in opposition to its value — has general validity in its given state as value. Not only had no one prior to Marx solved those riddles, there was not even an awareness that they are in fact riddles. Marx became the first to thoroughly clarify these problems by raising the theoretical question in Capital pertaining to the value-form. Marx perceived, first of all, that the money-form is the developed value-form. This means that the riddle of the money-form is nothing more than an extension of the fundamental riddle of the value-form. By tracing the money-form to its source, thereby reducing it to its elemental form, which is the simple value-form, Marx locates the core of the riddle of the money-form and of money: the fact that a commodity expresses its own value in the use-value of another commodity that it equates to itself, thereby making the use-value of that other commodity the form of its own value. This is precisely the riddle of the value-form, which is the basis of the riddle of the money-form and the riddle of money. Without unraveling the first riddle, it is quite impossible to unravel the latter two; whereas those riddles are easily unraveled once the former has been elucidated.
Samezō Kuruma, “Marx’s Theory of the Genesis of Money”, Part One, “Theory of the Value-Form and Theory of the Exchange Process”, 1957.