f it constantly, under all circumstances, of an equal value, then the
degree of value of all things, ascertained by such a fixed standard,
would vary according to the proportion _betwixt the quantity of them_,
and the demand for them, and every commodity would of course be subject
to a variation in its value, from four different circumstances.

1. "It would be subject to an increase of its value, from a diminution
of its quantity.

2. "To a diminution of its value, from an augmentation of its quantity.

3. "It might suffer an augmentation in its value, from the circumstance
of an increased demand.

4. "Its value might be diminished by a failure of demand.

"As it will, however, clearly appear that no commodity can possess fixed
and intrinsic value, so as to qualify it for a measure of the value of
other commodities, mankind are induced to select, as a practical measure
of value, that which appears the least liable to any of these four
sources of variations, _which are the sole causes of alteration of
value_.

"When in common language, therefore, we express the _value_ of any
commodity, it may vary at one period from what it is at another, in
consequence of eight different contingencies.

1. "From the four circumstances above stated, in relation to the
commodity of which we mean to express the value.

2. "From the same four circumstances, in relation to the commodity we
have adopted as a measure of value."[50]

This is true of monopolized commodities, and indeed of the market price
of all other commodities for a limited period. If the demand for hats
should be doubled, the price would immediately rise, but that rise would
be only temporary, unless the cost of production of hats, or their
natural price, were raised. If the natural price of bread should fall 50
per cent. from some great discovery in the science of agriculture, the
demand would not greatly increase, for no man would desire more than
would satisfy his wants, and as the demand would not increase, neither
would the supply; for a commodity is not supplied merely because it can
be produced, but because there is a demand for it. Here then we have a
case where the supply and demand have scarcely varied, or if they have
increased they have increased in the same proportion; and yet the price
of bread will have fallen 50 per cent. at a time too when the value of
money had continued invariable.

Commodities which are monopolized, either by an individual, or