Dean Kenning << >> Chapter 1: The Commodity Page 127 [...] exchange-value cannot be anything other than the mode of expression, the 'form of appearance', of a content distinguishable from it. [...] for instance 1 quarter of corn = x cwt of iron. What does this equation signify? It signifies that a common element of identical magnitude exists in two different things, in 1 quarter of corn and similarly in x cwt of iron. Both are therefore equal to a third thing, which in itself is neither the one nor the other. Each of them, so far as it is exchange-value, must therefore be reducible to this third thing.