A proper name, when used in business or in pleading, 2 means one individual thing, and no other, as every one knows, and therefore one to whom such a name is used must find out at his peril what the object designated is.  If there are no circumstances which make the use deceptive on either side, each is entitled to insist on the [310] meaning favorable to him for the word as used by him, and neither is entitled to insist on that meaning for the word as used by the other.  So far from mistake having been the ground of decision, as mistake, its only bearing, as it seems to me, was to establish that neither party knew that he was understood by the other to use the word “Peerless “in the sense which the latter gave to it.  In that event there would perhaps have been a binding contract, because, if a man uses a word to which he knows the other party attaches, and understands him to attach, a certain meaning, he may be held to that meaning, and not be allowed to give it any other. 1

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