10. PAULUS libro v ad Sabinum.

Aliter atque si aurum quidem fuerit, deterius autem quam emptor existimaret: tunc enim emptio ualet.

view, there may be a mistake as to what is here called its substantia, and elsewhere (LL. 11 and 14) its materia, that is, error as to its quality or material attributes. The name error in substantia has often been inappropriately applied to this kind of mistake, as if it always concerned the material or substance of which the thing is made, and were always to be regarded as essential; whereas an error as to the qualities of the material, its goodness, etc., was called error in bonitate, and was held, as a rule, to be non-essential. But Savigny has shown that this distinction is irrelevant, though logically correct: for instance, if a buyer thinks a female slave is a male slave, the sale is void, yet the idea of a difference of materia or substantia between the sexes is out of the question. Similarly, in all the examples put by the jurists of a sale being rescinded on account of a mistake about the materia, Savigny finds that the rule rests on something else than the abstract-idea of substance (ovoía); and he lays down a principle, which has been generally approved in spite of the difficulties presented by one or two of the texts referred to above, viz. that an error of this kind is essential when a quality is wrongly attributed to the subject-matter of the agreement, in virtue of which the thing would, according to the ordinary ideas and language of trade, fall under a different category of merchandise from what it actually belongs to. In other words, a sale is not void unless the difference between the thing sold, as it is, and as it is mistakenly supposed to be, amounts to a difference in kind, according to the ordinary classification of commodities; for then, as Ulpian puts it, aliud pro alio venisse videtur. Sav. Syst. iii. §§ 137, 138.

In the examples here given, the words aurum aes, etc., probably mean vessels of gold, bronze, etc., and not the unwrought metal, which could not so readily be mistaken. Cp. L. 14. The mistake of a base metal for a precious metal avoids the contract, even though the article be plated (L. 41, 1), because gold and silver articles are a special class of goods, of high intrinsic value apart from the workmanship, and the workers in these metals form a class quite distinct from coppersmiths or plumbers. Appar

10. PAUL.

It is different when the thing sold is really gold, but of poorer quality than the buyer thought; in that case the sale stands.

ently Marcellus (like Labeo, quoted by Marcian in L. 45) held the view that error in materia did not rescind the contract-an opinion superseded by that of Ulpian; indeed they are not really in agreement even to the extent stated in the text, for Ulpian distinguishes bad wine from stuff that is not wine at all, and upholds the sale of the former for the same reason as Paul upholds the sale of inferior gold (L. 10), whereas the sale would stand in both cases according to Marcellus, but for a different reason.

A mistake about the fineness of gold is not essential, because gold may be more or less alloyed without ceasing to be gold in the ordinary trade sense (L. 10).

Savigny explains the case put in L. 11, 1 (cp. 19. 1. 11, 5) in the same way: mistake about the sex of a slave is essential, because male and female slaves were looked on as different kinds of merchandise. It is not the distinction of sex, but the difference of employment that is material: female slaves were employed in household work, male slaves in trades and agriculture.

For mistake as to other particulars, the nature of the transaction, the price, etc.,-see Vangerow, § 604.

A good selection of English cases on Mistake will be found in Finch's Select Cases, pp. 466 sq.: one or two may be cited here in which analogies drawn from the civil law were employed. In Gompertz v. Bartlett (1853) 2 E. & B. 849, the purchaser of what purported to be a foreign bill of exchange, but was really a domestic bill and worthless because unstamped, was held entitled to recover the price from the vendor on the ground that the article did not answer the description of that which was sold, viz. a foreign bill. The case is precisely as if a bar was sold as gold, but was in fact brass, the vendor being innocent. In such a case the purchaser may recover.' This statement is scarcely definite enough: what is implied in pro auro,' as gold,' is (1) a mistake common to the buyer and seller, each believing that the subject-matter is gold, and (2) a mutual intention to contract about gold and nothing else. Cp. L. 14 infra. But the ground of judgment in the case cited was not so much mistake, as failure to deliver a genuine article marketable by the name used in describing it;

11. ULPIANUS libro XXVIII ad Sabinum.

Alioquin quid dicemus, si caecus emptor fuit uel si in materia in erratur uel in minus perito discernendarum materiarum? corpus eos consensisse dicemus ? et quemadmodum consensit, qui non uidit?

ceterum

1. Quod si ego me uirginem emere putarem, cum esset iam mulier, emptio ualebit: in sexu enim non est erratum. si ego mulierem uenderem, tu puerum emere existimasti, quia in sexu error est, nulla emptio, nulla uenditio est.

for it is well settled that a sale under a particular description is equivalent to a condition precedent to the vendor's right of action, and, if something else is delivered instead of the described article, the buyer may reject, and recover the price if paid. Cp. S. G. B. § 15: Where there is a contract for the sale of goods by description, there is an implied condition that the goods shall correspond with the description.' Where, however, the article tendered answers the description, the buyer must, in the absence of fraud and warranty, take it with all faults. In Wieler v. Schilizzi (1856) 17 C. B. 619, there was a contract for the sale of Calcutta linseed, and it was held the buyer had a right to expect an article saleable in the market as such. If a man buys an article as gold, which everyone knows requires a certain amount of alloy, he cannot be said to get "gold" if he gets an article so depreciated in quality as to consist of gold only to the extent of one carat.'

The rule governing all questions of mistake as to the subjectmatter of the contract is fully explained in Kennedy v. Panama Mail Co. (1867) L. R. 2 Q. B. 580. An innocent misrepresentation or missapprehension does not authorise a rescission unless it is such as to show that there is a complete difference in substance between what was supposed to be and what was taken, so as to constitute a failure of consideration.' After referring to LL. 9-11, Lord Blackburn proceeds: The principle of our law is the same as that of the civil law; and the difficulty in every case is to determine whether the mistake or misapprehension is as to the substance of the whole consideration, going, as it were, to the root of the matter, or only to some point, even though a material point, an error as to which does not affect the substance of the whole consideration.'

11. ULPIAN.

Can

But what if the buyer was blind, or if he mistook the material, or lacked experience in discriminating between materials? we say that the parties are agreed upon a specific thing? how can there be assent by one who has not seen the thing?

But

1. If I buy a female slave supposing her to be a virgin, when she is not so, the sale will stand; for there was no mistake about the sex. But if I sell you a woman, and you suppose you are buying a slave boy there is no contract, because there is a mistake about the sex.

With Ulpian's example of a female slave thought to be a virgin when she was not, he compares Street v. Blay, 2 B. & Ad. 456, where it was held, in the case of a horse supposed to be sound but not really so, that if the belief was induced by an honest misrepresentation as to its soundness, though it may be clear that both vendor and purchaser thought that they were dealing about a sound horse and were mistaken, yet the purchaser must pay the whole price, unless there was a warranty. If the misapprehension relates only to some quality or accident, even though that may have been the actuating motive to the purchaser, yet the contract remains binding.

It should be noted that by English law a sale will not be avoided by the mistake of one side alone as to a material attribute, unless produced by the other party. The same law seems laid down for Scotland in Stewart v. Kennedy (1890) 15 App. Ca. at p. 121, 'in the case of onerous contracts reduced to writing, the erroneous belief of one of the contracting parties, in regard to the nature of the obligations which he has undertaken, will not be sufficient to give him the right to rescind, unless such belief has been induced by the representations, fraudulent or not, of the other party to the contract;' and in Smith v. Hughes (1871) L. R. 6 Q. B. 597, it was observed that passive acquiescence of the seller in the self-deception of the buyer does not entitle the latter to avoid the contract. In the civil law, on the contrary, the sale was always avoided by the buyer's essential error, no matter whether the seller shared in it or not, and in the latter case, whether he was passively acquiescent in or actively furthered the misconception. See further, Pollock, Contract, p. 464 sq.

C

12. POMPONIUS libro XXXI ad Quintum Mucium.

In huiusmodi autem quaestionibus personae ementium et uendentium spectari debent, non eorum quibus adquiritur ex eo contractu actio: nam si seruus meus uel filius qui in mea potestate est me praesente suo nomine emat, non est quaerendum, quid ego existimem, sed quid ille qui contrahit.

13. POMPONIUS libro IX ad Sabinum.

Sed si seruo meo, uel ei cui mandauero, uendas sciens fugitiuum, illo ignorante, me sciente, non teneri te ex empto uerum est.

14. ULPIANUS libro XXVIII ad Sabinum.

Quid tamen dicemus, si in materia et qualitate ambo errarent? ut puta si et ego me uendere aurum putarem et tu emere, cuin aes esset? ut puta coheredes uiriolam, quae aurea dicebatur, pretio exquisito uni heredi uendidissent eaque inuenta esset magna ex parte aenea? uenditionem esse constat ideo quia auri aliquid habuit. nam si inauratum aliquid sit, licet ego aureum putem, ualet uenditio: si autem aes pro auro ueneat, non ualet.

LL. 12, 13.-See for details as to the contractual capacity of a slave or filiusfamilias, Inst. ii. tit. 9; iii. tit. 17 and 28; and as to the liabilities arising from their contracts, iv. tit. 7. Though the owner or father took all benefit and got the title to sue on the contract, yet if any question affecting its validity arose, it was only the actual contractor's intention and information that were relevant. Of course, if the slave acted merely as a 'nuntius or intermediary between his owner and the other party, the contract is in reality the owner's, and he can sue or be sued directly. The case contemplated in L. 12 is where the son or slave contracts in his own name with the knowledge of his pater or dominus, but without express authority (jussus).

In L. 13 the case is one of authorised agency; a slave or an 'extranea persona' buys a slave for his principal in virtue of a mandate, and a question arises as to a vitium affecting the slave. Here the knowledge of the contracting party is plainly the material fact. (a) If the mandatary knows the slave to be a runaway, it matters not whether the mandant knows or not; no action is