Juan de Mariana, De monetæ mutatione (1609)
The thirteen-chapter treatise in which a Jesuit historian argued that debasing the coinage is a tax levied without consent, and therefore theft; that money has two values which a well-ordered commonwealth must keep equal; and that prices rise by as much as is taken out of the coin. He argued it from Castilian statute and from a price history of four earlier debasements, refused the same reasoning's application to the American silver, and printed the case against himself in his own chapter IX.
Why this wins its question: English-language coverage of this treatise is almost entirely secondary and almost entirely partisan: it appears as a founding text of one modern school of economics, quoted through translations of translations, or as a footnote to Mariana's separate defence of tyrannicide. Neither kind of account opens the book. This object quotes the Latin from the first edition — Cologne, Antonius Hierat, 1609 — read page by page as scans, gives the treatise's own thirteen-chapter index, and separates what is usually run together: the consent argument, the two-values analysis, the price history he used as evidence, and the explicit method statement that he preferred worked examples to theory. It also records the three things the partisan accounts drop — that he conceded an emergency power to debase with a duty of restitution, that he named the royal monopolies and then declined to challenge them, and that he printed a chapter on the advantages of the copper coinage and conceded one of his own arguments was two-edged.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
The treatise was printed as the fourth of seven tracts issued together at Cologne in 1609. The title page reads "IOANNIS MARIANAE E SOCIETATE IESV TRACTATVS VII", lists them — "I. De Aduentu B. Jacobi Apostoli in Hispaniam. II. Pro Editione vulgata. III. De Spectaculis. IV. De Monetæ mutatione. V. De Die mortis Christi. VI. De Annis Arabum. VII. De Morte & Immortalitate" — declares them "Nunc primum in lucem editi", and gives the imprint "COLONIAE AGRIPPINAE, Sumptibus Antonij Hierati, sub Monocerote, Anno M.DC.IX." The monetary tract opens at page 189 under its own head "IOANNIS MARIANAE. DE MONETÆ MVTATIONE. DISPVTATIO?" with a CAPITVM INDEX of thirteen chapters.
The argument is built from the ground up, not asserted. Chapter I asks "Num Rex sit dominus bonorum quæ subditi possident" — whether the king is owner of the goods his subjects hold — and chapter II "An Rex possit tributa subditis imperare non consentientibus". The conclusion of chapter II is stated as a fixed rule: "Sit ergo fixum nunquam Principi licere subditos nouis oneribus premere, nisi accedat consensus quorum interest, certè populi capitum & reipublicæ", with the ground given immediately — "in Regis arbitrio non esse priuata ciuium bona. Non ergo aut vniuersa aut partem decerpet nisi ex eorum voluntate, quorum in iure sunt." The chapter closes on the universal form: "nullus est Rex aut Princeps in orbe terrarum, qui possit à gente sua, vel quadrantem vnum exigere nisi volentibus qui debent repræsentare, nisi per violentiam & tyrannidem."
He grounds the rule in Castilian positive law rather than in theology alone. Chapter II cites the law Alfonso XI granted at the cortes of Madrid in 1329 on the people's petition 68, "ne vnquam iniussu populi tributum genti imponatur", and prints its words: "Adhæc quoniam supplices postularunt, ne insolutum tributum imperetur, neque publicè, neque priuatim nisi gente in conuentum prius vocata, concessoque ab omnibus procuratoribus ciuitatum qui aderunt: ad hoc respondemus: placet id nobis, atque vt ita fiat statuo." He adds that the monetary laws of Ferdinand the Catholic, of Philip II and of the earlier kings were, so far as he can find, always passed in the assemblies of the realm — "in gentis conuentibus semper fuisse latas inuenio".
He extends the same consent requirement to monopolies, and then declines to press it. Chapter II holds "monopolia à tributis non discrepare, neque minori cautione opus fore vt ea rite instituantur, neque minori populi consensu", and names the royal monopolies then standing — playing cards, sublimate and salt, "aleatoriarum chartarum, sublimati, atque salis". Of those he writes "De quibus non disputo: ac prudenter potius institutam arbitror, & de Principis probitate & religione credendum, nihil in eo commisisse quod à ratione quod à legibus exorbitaret." The general rule is pressed; the standing instances of it are excused.
The identification that carries the treatise is made in chapter III, "Num Rex monetam vitiare possit pondere aut bonitate mutatis, populo inconsulto". Debasement is not like a tax; it is one. "Nam si Rex bonorum, quæ subditi priuatim possident, rector & non arbiter est, neque hac neque alia ratione & arte poterit eorum partem decerpere pro voluntate: quod contingit quoties vitiatur moneta: pluris enim datur, quod valet minus." And therefore: "Quod si Princeps subditis tributa imperare non potest inuitis, neque rerum venalium monopolia instituere, non poterit ex moneta adulterata nouum lucrum captare: eodem enim pertinent hæ artes ad emungendum populi marsupia." The warning against the disguise is explicit — "ne fuco capiaris & fraude, metallo dantis legis maiorem valorem, quam pro sua natura & communi æstimatione."
The rule is not absolute, and the exceptions are stated in the same chapter rather than buried. Two things are conceded at the head of chapter III: the king may freely change the form and the image struck on the coin, "modo eam deteriorem solito non efficiat"; and under the pressure of war or siege "Regem damus posse sine populo vitiare monetam, modo vitium non vltra tempus angustiæ prorogetur, rebusque tranquillis integra fide satisfaciat ijs qui damnum pertulerunt" — the emergency power is bounded in time and carries a duty of full restitution. The precedents offered are of rulers who honoured it: Frederick II struck leather money at the siege of Faenza and afterwards "integra fide pro coriaceis monetis totidem aureos nummos reposuit", and Leiden under siege struck money from paper in 1574.
Chapter IV, "Geminus pecuniæ valor", sets out the analytical core. Money has two values: "alter intrinsecus & naturalis ex metalli conditione & pondere sumptus, quibus accedat cudendi labor & apparatus non sine sumptu susceptus; alter legalis vocatur & extrinsecus nempe lege Principis constitutus". Keeping them equal is a duty of government: "In bene constituta republica penes quos rerum arbitrium, ijs curæ esse debet, vti hi duo valores exæquentur neque discrepent inter se: nam vt esset iniquum in alijs mercibus quod ex se atque communi æstimatione valet nummos quinque, taxare decem, tantundem in pecunia contingit si legalis valor exorbitet." Elsewhere he states the same aim as a rule of minting practice — "quod est legalem valorem naturali adaptare".
Chapter IX opens with an explicit statement of method that is unusual for a theological treatise of 1609: "IN re grauissima æquum est, non ex meo capite & cogitationibus subtilia & theorica ducere argumenta, quæ fucum sæpè faciunt, sed exemplis potiùs pugnare rerum gestarum nostra aut maiorum ætate. Eam rationem tutissimam puto, viamque ad veritatem certam, quoniam præsentia tempora haud dubium præteritis sunt similia." He returns to it when summarising his objections as "non ab inanibus cogitationibus profecta, sed vsu priorum temporum & memoria antiquitatis comprobata."
The evidence he actually brings is a price history of earlier Castilian debasements. Under Alfonso X the good "pepiones" current at Burgos were replaced with less good coin; a general rise in prices followed; as a remedy the king fixed by law what every commodity should sell for, and the remedy failed — "Medicina malum recruduit mercatoribus eo pretio vendere recusantibus. Itaque necessario destiterunt", the merchants refusing to sell at the tariff so that it had to be abandoned. Under Henry II, the treasury exhausted by the war against his brother Pedro, a twin coinage of "regales" at three maravedís and "cruciados" at one was struck: "Creuit ex eo annona, creuêre res aliæ. Aureus quem duplam dicebant, ad 300. Marauedinos peruenit, equus 60000. emebatur", and by the sixth year of the reign a horse had reached 80,000 maravedís, after which the prince cut two thirds from the legal value of both coins.
From that record he states the quantitative claim. The third harm of the copper alteration will be "mercium caritatem omnium non minorem breui futuram, quàm quod est de pecuniæ bonitate & pondere detractum" — a rise in the price of all goods, shortly, no smaller than what has been subtracted from the coin's fineness and weight (the printing contracts the terminal -m of several of those words with a tilde). He notes that the attempt to hold silver at its old rate, "atque octo vnciæ æstimarentur 125. Marauedinis, vt antè non amplius", accomplished nothing: "Quæ cautio præstitit nihil, subsecuta rerum caritate, aucto argenti pretio."
He also records a dated observation of the metal market answering the mint. Copper that a few years earlier sold in France at eighteen francs the hundredweight — so that eight ounces, "quod nos pondus marcum dicimus", cost thirteen maravedís, and less again in Germany — now stood in Castile at forty-six maravedís for the same weight, "quod pretium indies crescet cudendi monetam æream sine fine necessitate, aut potius auiditate": a price he expects to rise daily because of the endless coining of copper, from necessity or rather from greed.
The case against his own position is printed inside the treatise rather than omitted from it. Chapter VII is titled "Commoda quæ ex mutatione æreæ monetæ proueniunt" — the advantages that come from the change. And where an objection cuts both ways he says so: against the argument that men will leave the land untilled when the only reward offered is debased coin, he sets the opposing case that abundant copper puts coin within everyone's reach so that the produce of land and craft reaches market, "antea ob inopiam pecuniæ sæpè neglecta", and concludes "Ita ex hoc capite argumentum ducitur anceps: & quoniam in vtramque partem verti potest, in alterutram magnam vim non habet." He likewise grants that the copper coinage does not prevent "quotannis magna vis argenti ab Indis veniat".
Chapter XI, "Num argentea pecunia mutari debeat", turns the argument on the American silver and refuses the yield. He states the gain plainly: if a million marks of silver come every year from the Indies by the annual navigations, altering the standard would bring at least five hundred thousand gold pieces a year into the treasury, a revenue whose capitalised value he reckons at ten million gold pieces, "nostro more dixeris decem milliones, Romano quatermillies sestertium". He refuses it on two grounds. The mechanism: "argentum rude necessario deprauata moneta maioris constabit quam antè, quantum de bonitate monetæ detractum fuerit nihilominus" — unwrought silver will simply cost more by exactly the amount taken out. And the systemic risk: "Compages hæc rerum subtilissimarum tot annorum spatio coaluit: neque conuelli poterit, vt ego arbitror, sine conuellentium & totius prouinciæ exitio."
The same chapter puts the Spanish silver standard on the record as a matter of statute. He notes it has long been observed in Spain "vt argentum signetur vndecim graduum (quos gradus denarios vocant monetarij) & quatuor granorum, nempe admixtis viginti æris granis non ampliùs. Sic constat ex legibus regni monetarijs", that the goldsmiths keep the same fineness in unwrought silver and in the vessels they make, and that the standing law is the one Juan II of Castile promulgated at the cortes of Madrid in 1435, petition 31, "Quæ lex proxima est nouæ recopilationis part. I. libr. V. titul. XXII."
What this evidence carries should be stated plainly. The 1609 printing is the argument, not its sequel: it shows what Mariana published, in what words, with which authorities and which price data, and it shows him printing the counter-case. It does not show how the treatise was received, what happened to its author, or whether the Castilian vellón inflation of the following decades bore out his prediction. No claim here should be read as evidence of any of those things.