A commodity is any good or service that is useful as an input in production
or con- sumption and can be exchanged with other goods or services. The
exchangeability of commodities presupposes the existence of a common
element that makes them commen- surable to each other. Classical economists
argued that the common element contained in commodities is that they are
products of labour. Hence, the quantity of labour time spent to produce any
commodity becomes the measurement stick of its worthiness. Of course, there
are differences and qualifications within this broad classical approach.
For example, Marx's concept of abstract socially necessary labour time -
that is, the labour time without its specific characteristics - is what
gives worthiness to commodities.
Historically certain commodities, owing to certain useful attributes they
possessed, became money commodities; that is, the means through which the
other commodities can express their worthiness and in doing so become the
medium for quoting prices. If gold, for example, is the money commodity,
the other commodities express their worthiness in terms of a certain quantity of gold (for example, 1 US dollar 5
1/4 ounce of gold). The value - to wit, the abstract socially necessary labour time -
contained in a commodity, relative to the value of gold, gives the direct
price or a first approximation of the monetary expression of value and a
centre of gravity for observed (market) prices (Shaikh, 1980).