Next, suppose a case in which the offer and acceptance do not differ, and in which both parties have used the same words in the same sense. Suppose that A agreed to buy, and B agreed to sell, "these barrels of mackerel," and that the barrels in question turn out to contain salt. There is mutual mistake as to the contents of the barrels, and no fraud on either side. I suppose the contract would be void. /2/ It is commonly said that the failure of the contract in such a case is due to the fact of a difference in kind between the actual subject-matter and that to which the intention of the parties was directed. It is perhaps more instructive to say that the terms of the supposed contract, although seemingly consistent, were contradictory, in matters that went to the root of the bargain. For, by one of the essential terms, the subject-matter of the agreement was the contents of certain barrels, and nothing else, and, by another equally important, it was mackerel, and nothing else; [311] while, as a matter of fact, it could not be both, because the contents of the barrels were salt. As neither term could be left out without forcing on the parties a contract which they did not make, it follows that A cannot be required to accept, nor B to deliver either these barrels of salt, or other barrels of mackerel; and without omitting one term, the promise is meaningless. If there had been fraud on the seller's part, or if he had known what the barrels really contained, the buyer might have had a right to insist on delivery of the inferior article. Fraud would perhaps have made the contract valid at his option. Because, when a man qualifies sensible words with others which he knows, on secret grounds, are insensible when so applied, he may fairly be taken to authorize his promisee to insist on the possible part of his promise being performed, if the promisee is willing to forego the rest. Take one more illustration like the last case. A policy of insurance is issued on a certain building described in the policy as a machine-shop. In fact the building is not a machine-shop, but an organ factory, which is a greater risk. The contract is void, not because of any misrepresentation, but, as before, because two of its essential terms are repugnant, and their union is insensible. /1/ Of course the principle of repugnancy last explained might be stretched to apply to any inconsistency between the different terms of a contract. It might be said, for instance, that if a piece of gold is sold as eighteen-carat gold, and it is in fact not so pure, or if a cow is sold as yielding an average of twelve quarts of milk a day, and in fact she yields only six quarts, there is no logical difference, [312] according to the explanation which has just been offered, between those cases and that of the barrel of salt sold for mackerel. Yet those bargains would not be void. At the most, they would only be voidable, if the buyer chose to throw them up.