Contracts then purported to be made by spoken or written words apparently expressing a true consent are, as a rule, void if there be no real agreement of the parties' minds in some point which goes to the whole substance of the contract (k). Thus on an apparent agreement for the sale of land, if the parties' minds be not at one, owing to a mistake made on either side with regard to the nature of the transaction, the personality of the other contractor or the property to be sold, there is no contract between them. But if the party mistaken have expressed himself in words which are free from ambiguity and are apt to constitute a valid contract if taken in the meaning which they would naturally convey to a man of ordinary intelligence, then he is estopped from showing that his mental intention was not in accordance with his overt act (l). To give examples, first, as to mistake in the nature of the transaction. If one sign a contract for the sale of land under the impression that he is executing an entirely different kind of instrument, for example, a mortgage or charge, the contract is void, because the man's intention did not accompany his act (m). It is very difficult, perhaps impossible, to put a concrete case of this kind in which the mistake has not been caused by the fraud of the other party to the alleged agreement, or by the fraud, negligence or unauthorised interference of a third person, and yet the party mistaken is not estopped from proving his mistake; and, as we shall see, he may be estopped by reason of his negligence where the third person wrongfully misled him: but the rule is clearly established where the mistake was made in consequence of the other party's or by a third person's fraud. Thus if a blind or an illiterate man, or even a man free from any physical defect and of ordinary understanding, be induced by the fraud of some person minded to entrap him into a contract, or by the fraud of his own solicitor or servant or some stranger, to sign a contract for sale of his land under the impression that he is executing some document of an entirely different nature, the document is altogether void. It is not his act, for he never intended to utter such a document, and the case is exactly the same as if his signature had been forged (n).

Mistake on some point going to the whole subject of the contract.

Raffles v. Wichelhaus.

Estoppel by manifestation of a particular intention.

(k) Kennedy v. Panama, etc. Mail Co., L. R. 2 Q. B. 580, ,538; above, p. 667.

Mistake in the nature of the transaction.

(l) Above, p. 668.

(m) Thoroughgood's case, 2 Rep. 9; Simons v. Great Western Ry. Co., 2 C. B. N. S. 620; Foster v. Mackinnon, L. R. 4 C. P. 701; Lewis v. Clay, 67 L. J. Q. B. 224. The law is the same as regards the execution under a mistake of a deed of conveyance or any other deed; Thoroughgood's case, ubi sup.; Pigot's case, 11 Rep. 26b, 27b; see below, pp. 673, 674.

(n) See previous note. As to forgery, see next Chapter, Sec. 1, at end.

Or it may be likened to the case where a man, who has received an offer of sale or purchase of land, writes a letter of acceptance, hut, being in doubt whether he will send it, places the letter in a drawer to remain there until he shall reconsider the matter (o), and a third party without the writer's authority takes the letter from the drawer and sends it to the person who made the offer; in which case it is submitted that no contract is concluded between the parties (p). In these instances there is no reason why the party mistaken should be estopped from proving that his intention did not accompany his apparent act; he has not held himself out as expressing a contractual intention, nor has he been guilty of negligence (q). And it will be observed that in the cases where the mistake was caused, not by the other contractor's fraud but by the wrongful or improper intervention of a third person, the party mistaken is at liberty to prove that his intention did not accompany his outward act, notwithstanding that the mistake was on his side only, the other party truly intending to contract as expressed in the apparent agreement. But where a man makes a mistake of this kind solely by his own inadvertence, he will in general be precluded from alleging it. Thus it is submitted that if one in absence of mind sign and send a letter accepting an offer of sale or purchase, in the belief that he is accepting an invitation to dinner, he is bound. 80 also it is contended that, where a man, who has written a letter accepting an offer, but intends not to send it until he has reconsidered the matter, by his own inadvertence posts the letter or gives it to another to post, he would be estopped, after the letter had been posted (r), from showing that he did not intend to contract as expressed in the letter (s). Similarly, when a man knows that he is executing at his solicitor's instance a document which will have some legal consequence - which will be an act in the law on his part - but he does not ask what will be its exact effect, and has such confidence in his solicitor that he is content to execute it in ignorance, then the document is not void; though it may be voidable for fraud, if his solicitor fraudulently misled him (t). And in this case the validity of the document, where it binds the party to some transaction into which he did not intend to enter, appears to depend on estoppel; the man's intention did not really accompany his act, but he is precluded by his own negligence from setting-up this objection. So also, if a man execute a document intended to carry out some legal transaction, of the general nature of which he is well aware, such as the sale of his land, he cannot be heard to say that he did not understand the legal effect of the words used, or that he did not mean to enter into the legal obligations or do the legal acts, which according to the proper legal construction of those words are thereby expressed to be undertaken or done (u). As we have seen (x), the case, where a man executes a legal instrument by mistake under the impression that he is entering into some transaction entirely different from that evidenced by the instrument, must be carefully distinguished from that where he is induced to make a contract or conveyance by a fraudulent misrepresentation as to some fact, other than the nature of the transaction contemplated. In the one case, if the man is not estopped from proving that his intention did not accompany his overt act, the instrument is void (y). In the other, he did really intend, at the time of executing the document, to make the contract or conveyance therein expressed: but he would not have had this intention if he had known the truth as to the fact misrepresented (z). The document is therefore voidable by him, but it is not altogether void from the outset (z). Attached to this distinction is the very important consequence, as regards the conveyance induced by such fraudulent misrepresentation of lands or goods, that if the person who has taken under such a conveyance dispose of the lands or goods to a purchaser for value taking in good faith without notice of the fraud, the conveyance procured by fraud is not voidable as against the purchaser (a).