¹ I would like to thank Massimo Amato, Torbjörn Engdahl, Akinobu Kuroda, Anders Ögren, Sevket Pamuk, Om Prakash, Willem Wolters, and the other participants of workshops at NYU, Tokyo University and ENS Paris, for comments on earlier versions of this article.

² Along these lines, e.g., T. Guggenheim has retold the history of monetary thought as a progressive unfolding of the quantity theory (Preclassical Monetary Theories (New York, 1989)); and, more recently, Sargent and Velde have rewritten the history of monetary practices as a technical and theoretical evolution, leading to the gradual discovery of the standard formula, according to which modern central banks manage the supply of fiat money, to the point that, as they admit: ‘we may seem to be writing a history of how past monetary experts learned our model’ (The Big Problem of Small Change (Princeton, 2002), p. 14).

³ Other European states followed suit, minting large silver coins, of the value of one shilling, generally called grossi (grooten, groats, etc.), while the small penny coins were thenceforth called piccoli.

⁴ The diffusion of gold coinage took almost a century to spread throughout the Continent, but was equally extensive: M. Bloch, Esquisse d'une histoire monétaire de l'Europe (Paris, 1954).

⁵ C. M. Cipolla, Money, Prices, and Civilization in the Mediterranean World (Princeton, 1956).

⁶ E. Fournial, Histoire monétaire de l'Occident médiéval (Paris, 1970), p. 27.

⁷ L. Einaudi, ‘Teoria della moneta immaginaria nel tempo da Carlomagno a Napoleone’, Rivista di Storia Economica, 1 (1936).

⁸ P. Spufford, Money and Its Use in Medieval Europe (Cambridge, 1988), pp. 411–13. On the relevance of this distinction and on other historiographic interpretations, see section ii on ‘Unit of account and unit of payment’ in the contribution of Wolters to this issue.

⁹ Spufford, Money, Table 1, significantly entitled ‘The florin-ducat standard in the fifteenth century’.

¹⁰ And perhaps also other factors. See footnote 45.

¹¹ As I have tried to show in ‘Complementary currencies: a prospect on money from a retrospect on premodern practices’, Financial History Review, 12.1 (2005).

¹² This cannot be attributed to a change in the bimetallic ratio, which varied considerably, but not for the whole period in the same direction: C. P. Kindleberger, A Financial History of Western Europe (Oxford, 1993), p. 60.

¹³ Spufford, Money, pp. 402–6.

¹⁴ Ibid.

¹⁵ The need to distinguish between these two sorts of debasements is repeatedly stressed also by Spufford, Money, pp. 289, 308–18.

¹⁶ ‘Proper’ or ‘improper’ use, according to the terminology of M. Amato, ‘Notes on the (im)proper use of money. From an openly hidden tradition of money-thinking’, paper for the IEHC (Helsinki, 2006).

¹⁷ This provides the necessary incentive to bring coins back to the mint for recoinage, in a system in which old coins are only exceptionally demonetised and which is generally based on free coinage (A. Redish, Bimetallism: an Economic and Historical Analysis (Cambridge, 2000), p. 27). Only on the relatively rare occasion of a general recoinage does the public receive coins of a lower aggregate value than those surrendered (see below, footnote 28).

¹⁸ And, even in this case, what some lose is what others gain.

¹⁹ Spufford, Money, p. 303.

²⁰ See example for thirteenth-century England quoted by M. Prestwich, ‘Edward I's monetary policies and their consequences’, Economic History Review, 22 (1969), p. 411.

²¹ N. Sussman, ‘Debasements, royal revenues, and inflation in France during the Hundred Years’ War', Journal of Economic History, 53 (1993), p. 62.

²² D. H. Fischer, The Great Wave: Price Revolutions and the Rhythm of History (Oxford, 1996), p. 286; see also N. J. Mayhew, ‘Population, money supply, and the velocity of circulation in England, 1300-1700’, Economic History Review, 48 (1995), table 1.

²³ Y. S. Brenner, ‘The inflation of prices in early sixteenth century England’, Economic History Review, 14 (1961), pp. 230–1.

²⁴ D. Ricardo, The Principles of Political Economy and Taxation (London, 1817), The Works and Correspondence of David Ricardo, ed. P. Sraffa, vol. i (Cambridge, 1962), p. 353. The temporary character of price rises caused by monetary alterations in sixteenth-century England is also acknowledged by Fischer: ‘debasements caused inflationary surges but did not drive the underlying trend’ (Fischer, Great Wave, fig. 2. 13).

²⁵ Direct taxation provided a form of war finance less disturbing to monetary stability and distributive justice, and perhaps even more effective, as testified not only by England throughout its history, but also by France during the last phases of the Hundred Years War (R. Sédillot, Le franc (Paris, 1953), p. 73).

²⁶ Spufford, Money, p. 345.

²⁷ In any case, these costs must not have represented a significant part of the prince's expenditures. On the contrary, at the height of the bullion-famine, between 1457 and 1464, princes were prepared to mint black money at a loss (ibid., p. 361).

²⁸ Prestwich, ‘Edward I’, p. 407. A recoinage tax was thus levied by a periodic renovatio monetae in the central Middle Ages, not only in England, but also in Poland and Bohemia (Spufford, Money, pp. 94-105 passim).

²⁹ A. Hughes, C. G. Crump and C. Johnson, ‘The debasement of the coinage under Edward III’, Economic Journal, 7 (1897), p. 188.

³⁰ This appears to be consistent with the point made by Redish: ‘with the exception of a few spectacular episodes of debasement, the depreciation was not driven by fiscal objectives but by the objective of maintaining a circulation of coins trading at their legal tender value in the unit of account’ (Bimetallism, p. 9).

³¹ W. Täuber, Geld und Kredit im Mittelalter (Berlin, 1933), pp. 252–4.

³² Spufford, Money, app. 11.

³³ As testified e.g. for Piedmont, over four centuries, by the tariffs reproduced in V. Saraceno, Il corso delle monete seguito negli Stati di S.S.R.M. il Re di Sardegna … dal 1300 sino al presente (Turin, 1782).

³⁴ Accordingly, A. Redish relates the medieval ‘commodity-based money’ to the post-Bretton Woods fiat money in that, even by the former system, ‘the anchor [on money supply] was put in place not by fundamental natural forces but by decisions of human monetary authorities’ (‘Anchors aweigh: the transition from commodity money to fiat money in western economies’, Canadian Journal of Economics, 26 (1993), p. 778).

³⁵ This is suggested even by Anna Schwartz as a possible explanation for what she must acknowledge as an exception to the validity of the quantity theory: ‘In the final quarter of the fourteenth century the trend of prices was declining, though Navarre is an exception; the price rise there is attributable to deliberate monetary expansion that offset a decline in prices quoted in gold … Debasements and the marking-up of existing coinage apparently offset the deflationary forces’ (‘Secular price change in historical perspective’, Journal of Money, Credit and Banking, 5 (1973), p. 248).

³⁶ D. Hume, ‘On the balance of trade’, Political Discourses (Edinburgh, 1752).

³⁷ J. M. Keynes, The General Theory of Employment, Interest and Money (London, 1936), The Collected Writings of John Maynard Keynes, vol. vii (London, 1973), p. 349.

³⁸ C. P. Kindleberger, ‘The economic crisis of 1619 to 1623’, The Journal of Economic History, 51 (1991), p. 154.

³⁹ M. M. Postan, ‘The rise of a money economy’, Economic History Review, 14 (1944), p. 128.

⁴⁰ Subsidiary coinage was not always state money, issued and evaluated by a single authority, and its legal value was not necessarily enforced uniformly throughout a given political entity. The other articles in this issue suggest, in different periods or regions, the possibility that different forms of internal money could coexist under the same sovereignty.

⁴¹ W. Mitchell, ‘The role of money in economic history’, Journal of Economic History, 4 (1944), p. 63.

⁴² Despite the prevalence of the single-money doctrine in economic theory, the practice of complementary currencies proceeded even after the establishment of paper money, as shown, e.g., by the Swedish example described in this issue by Engdahl and Ögren.

⁴³ This point is clearly made by Kuroda, with a number of significant examples, in his contribution to this issue, as well as in ‘The Maria Theresa dollar in the early twentieth-century Red Sea region: a complementary interface between multiple markets’, Financial History Review, 14 (2007).

⁴⁴ Amato, ‘Notes’.

⁴⁵ As well as to other factors influencing the relative demand and supply of different coins for different purposes, such as fluctuations of the bimetallic ratio on international markets, or peculiar requirements of a specific coin for balance of payment settlements towards a specific area.

⁴⁶ It is the peculiar form of stability that determines the function of the coinage. Silver coins can be ascribed to one type or the other, according to which standard of value (extrinsic or intrinsic) they maintain. The fact that all coins maintain either one or the other confirms the significance of the double standard.

⁴⁷ See Einaudi, ‘Teoria’ and B. E. Supple, ‘Currency and commerce in the early seventeenth century’, Economic History Review, 10, (1957), p. 247.

⁴⁸ Spufford, Money, pp. 330–1.

⁴⁹ Thus, in striking accordance with the definition given by J. M. Keynes, Tract on Monetary Reform (London, 1923), p. 124.

⁵⁰ Spufford, Money, pp. 382–6.

⁵¹ M. T. Boyer-Xambeau, G. Deleplace and L. Gillard, Monnaie privée et pouvoir des princes: l'économie des relations monétaires à la Renaissance (Paris, 1986), pp. 184–7.

⁵² Once again (see above, footnote 49), the structure of this regime bears a striking conformity with the definition of money given by Keynes (A Treatise on Money, vol. i: The Pure Theory of Money (London, 1930), pp. 3–4). The monetary system of his time, and of ours, is not equally well described by this definition. Keynes distinguished throughout his work between ‘money as we know it’ and ‘money as it ought to be’. His contributions to rethinking and reforming money often refer, more or less explicitly, to history, not as a source of models or inspirations, but as the space where monetary institutions are established and where it is possible to see what in that establishing is at stake.

⁵³ Money and goods may be said to be complementary in the sense that there is a difference between them, and that there could not properly be one without the other. Goods are not money, they are not made to circulate indefinitely, and yet they could not be economic goods, i.e. commensurately exchanged, without the intermediation of money. Money is not a good, and yet it could not be a true medium of exchange if it didn't ultimately yield to goods.

The (horizontal) complementarity between currencies is grounded on the (vertical) complementarity between money and goods. It is this vertical complementarity that makes two currencies complementary, and not simply concurrent. If there is a need for, and not merely a casual concurrence of, two currencies, it is in order for each of them to be delimited and hence to disappear, in favour of the appearance of goods.