And, indeed, with all their refinements they have not, as we have seen, been able to solve the problem of Value after all; even when we allow them like duellists to select their own weapons. And this, again, is due to the fact - which our wheel would have made clear to them - that they have not seen when a commodity was on or off the wheel, as a possible basis of their arguments, if they were to be strictly scientific in character; as, for example, when Jevons selects old coins, or pictures by old masters, old unsaleable machines, or ships which have had to be 'scrapped' for old iron, etc., or Bohm-Bawerk his old wines, in proof of their theory of Value. For no commodity can be properly or legitimately the subject-matter of the science of Political Economy, which is not reproducible, or, in a word, which is not permanently on the market, so that it has a place both on the production and on the consumption side of the wheel, where the supply and demand can be compared. A thing for which there is a demand, - as an old coin, a violin, or picture by a dead master, - but no possibility of further supply, is economically dead; it is a mere curiosity, and the price that is paid for it is a mere psychological whim or caprice, and has nothing to do with the problem of economic value properly so called.

In the same way, an article which has been produced with much expenditure of time and labour, but for which there is no demand, - or if there is a demand, it is not a demand for the thing itself, and in its proper function, but for some other thing into which it can be resolved, as when a machine or ship is sold for old iron, - is also not on the wheel, and cannot be considered in any legitimate discussion of the problem of Value. All these figure only on the Consumption side of the wheel, but not on its Production side, as they are not reproducible; and so are not in touch on their Production side, with the men on the axle, to receive the stamp of market price; and although they are sold, it is true, and so bring a price, they cannot be said to have a scientific value, or a legitimate market price. For the essence of a scientific law of Value, like all other scientific laws, is that it enables us to foresee and predict something; but who can predict the price of a picture by Turner or Whistler, or of the original manuscript of a Burns or Tennyson, which may rise to anything to-day, or sink to nothing to-morrow, according to the private fancies or fashion of the hour?

So, too, no article that is subject to either absolute Scarcity or absolute Monopoly can figure in any scientific solution of the problem of Value. They either appeal to small sections of persons who will pay almost any price, for any and every reason except a business or economic one, - for ostentation, affectation, singularity, or obstinacy; or if they are articles in economic and daily use, their value is regulated by nothing but the power of the monopolists, by limiting their output, to force their own prices on the public; the price being modified only by the expediency of not drying up or diverting the demand to other things, by too great an extortion. These goods are technically on the market, and so are on the wheel, and circulate around it; but as the men on the axle can neither foresee the actions of these monopolists, nor control the supply of their goods, they are really not on the wheel as the subject-matter for the determination of scientific Value at all, - any more than the fifty per cent charged by the money-lenders to the necessitous, has anything to do with the scientific law of Interest.

But there is another advantage in our putting the problem of Value on our continuously revolving wheel, with its central axle, and spokes in touch with every side of its circumference, and in letting it be ground out as a dynamical problem dealing with quantities of definite products continually thrown on the wheel and continually taken off again; - and that is, that our wheel will, by its revolutions, bring to light, as we shall presently see, any hidden powers that may enter into market prices other than purely economic ones, by concentrating them in visible, tangible, masses, - powers which would otherwise escape detection when diffused over numberless individual transactions, in the same way as if you put a miscellaneous number of fluid ingredients into a cylindrical vessel, and make them revolve fast enough, they will separate out in layers, and in bulk sufficient to be estimated and scientifically determined; precisely as you can only find out the flaws or oversights in an invention, when the machine is set to work, or of a play, when it is actually set on the stage.

For no numbers of inspections of individual bargains would ever enable the public to know where a 'forced gain' had entered into the market price of the ordinary commodities or services with which Political Economy deals, inasmuch as no individual can ever know, - except in the case of notorious monopolies like diamonds, or Standard Oil, etc., where the output is admittedly restricted, or the market known to be manipulated, - whether the sum-total of the supply of a commodity, drawn perhaps from all quarters of the world, is permanently able to keep up with the demand, or not. That can only be known, if known at all, by the men of the central exchanges on the axle. But what is more important still, no individual can know from bargains conducted under 'free contract,' whether one division of the industrial community has the 'whip-hand,' and so the power of extortion, over another - except, perhaps, in such palpable instances as the power of capitalists over their workmen, where the power to wait of the one, and the immediate necessity of living of the other, gives the former a 'pull,' a 'forced gain' or power of extortion exercised by capital purely as such, over wages as such, - or the power of a small body of large landowners, over all other classes of the community, when they happen to have the full control of the market.