Another doctrine which must be considered in this connection is that of estoppel in pais. This doctrine, as now understood, precludes one who has made positive statements of fact to another, in reliance upon which the latter has acted, from denying their truth in any controversy between these two parties. That the misstatement shall have been either wilful or negligent is immaterial.25 The effect of Deny v. Peek 26 on the doctrine of estoppel was pressed upon the English Court of Appeal Boon after the decision of that case, but it was emphatically stated that the decision had no effect upon the doctrine of estoppel as previously understood.27 Lindley, J., explained the matter thus: "Estoppel is not a cause of action - it is a rule of evidence which precludes a person from denying the truth of some statement previously made by him." 28 And in the same case Bowen, L. J., repeats this formula in substance: "Estoppel is only a rule of evidence; you cannot found an action upon estoppel." 29
23 "That which does enforce the liability is this - that under the circumstances of this document being presented to the bank for the purpose of being acted upon, and being acted upon on the representation that the agent had the authority of the principal, which he had not, that does import an obligation - the contract being for good consideration - an undertaking on the part of the agent that the thing which he represented to be genuine was genuine. That contains every element of warranty."  A. C. 114, 118. This decision is interesting to compare with Heilbut v. Buckleton,  A. G. 30, where the court held that a representation by a seller in regard to the character of personal property sold did not make him liable as a warrantor, since he did not in terms promise. In other words, the doctrine that the representation express or implied of an agent that he has authority to act amounts to a warranty is accepted by the House of Lords, but the much older and more firmly established doctrine that a representation by a seller inducing the sale of goods amounts to a warranty is now denied
23 7 E. & B. 301, 8 E. & B. 647.
24 [19031 A. C. 114.
25 See suprci, Sec.692.
26 14 App. Gas. 337.
It is amusing to reflect on the ease with which Lord Bowen would have disposed of such a fiction if the harmonizing of decisions had required instead of forbidding him to do so. Estoppel is a rule of evidence m the same way that conclusive presumptions are rules of evidence. An estoppel, like a conclusive presumption, is a rule of substantive law masquerading as a rule of evidence. To speak of conclusive evidence of something admittedly false may be a useful formula, but it disguises the truth. An estoppel is in effect a conclusive admission of the truth of a non-existent fact. This supposed fact may be essential either for a cause of action, for a defense, or for a replication. As the fact is non-existent it is obvious that the admiss-sion and nothing else supplies the requirement which otherwise would be lacking. If the admitted non-existent fact alone creates a cause of action, defense, or replication, the admission or estoppel is the sole foundation, if other facts are needed in conjunction a partial foundation, of the cause of action, defense, or replication.
An estoppel then may be, and frequently is, either the sole or the main foundation of a cause of action. When a warehouseman states to an intending purchaser in answer to an inquiry that the seller has a certain quantity of goods stored in the warehouse, and relying on that statement the purchaser completes the bargain, the warehouseman is estopped to deny the truth of his statement.30 The only essential facts of the purchaser's case when he sues the warehouseman are the misrepresentation, his own reliance upon it, and perhaps a demand and refusal; and the allegation of these facts constitutes a perfect cause of action, wherever reformed pleading has reached such a state that nothing further is required of the plaintiff than to state the material facts upon which his claim is founded. Nor is it material that the warehouseman was neither fraudulent nor negligent.31 His statement relates to a matter about which he must have accurate knowledge at his peril, or refrain from talking about it. So where a bailee issues a receipt for goods never received, and a purchaser relies upon the statement in the receipt that goods have been received.32 Or where a bailee fails to take up a receipt or bill of lading which mercantile usage requires him to take up when the goods behind the document are delivered, and in consequence a purchaser of the outstanding document is deceived by the representation which it contains that the bailee still holds the goods described, and is induced to buy the document or to advance money on the faith of it.33 Or where a corporation issues a certificate of stock to one who is not a shareholder, and a subsequent purchaser, relying upon the misrepresentation of the certificate, buys it.84 Or where a trustee, applied to for information as to the property of his cestui que trust by one proposing to lend money to the latter, gives misinformation, reliance upon which causes damage to the lender.'5 In all these cases, and their number might easily be increased, a cause of action exists because of damaging misrepresentation, certainly without regard to any fraudulent intent, and probably without regard to any other negligence than necessarily exists when a person whose position qualifies him to have accurate knowledge about a matter makes a misstatement in regard to it.
27 Tomkinsoa v. Balkis Consolidated Co., (1891] 2 Q. B. 614; Low v. Bou-verie, 11891] 3 Ch. 82.
28 Low v. Bouverie,  3 Ch. 82, 101.
29 Low v. Bouverie,  3 Ch. 82, 105. .
"It may seem difficult to suppose that such a situation can arise without negligence, but the English decisions seem to show the possibility, holding, as they do, that the warehouseman is estopped by such a representation when the only lack of accuracy in it is the omission to state that the seller has mingled in a mass a quantity of goods larger than that which the buyer proposes to purchase.
32 Williston, Sales, Sec. 419.
34 Tomkinson v. BaUds Consolidated Co.,  2 Q. B. 614; In re Ottos Kopje Diamond Mines,  1 Ch. 618.
35 Burrowes v. Lock, 10 Ves. 470; Brownlie v. Campbell, 5 App. Cas. 925, 953. In Low v. Bouverie,  3 Ch. 82, the Court of Appeal did not dispute the correctness of this doctrine, but construed the representation made by the trustee as amounting to no more than a statement of the trustee's belief, not a positive assertion of fact.
It is difficult to see how the law of estoppel and the doctrine of Deny v. Peek 36 can be kept permanently in separate compartments when law and equity are fused and pleading reduced to a mere statement of the facts of the case. An inquiry which may be made in this connection is what would have been the result of an action against the defendants in Deny v. Peek for failing to utilize as directors, on behalf of the corporation whose rshares the plaintiff had bought, the right to use steam as a mo-Hive power for its cars. It may be assumed that the value of the property would have been enhanced by the use of such motive power and that the directors, therefore, would have been liable if they had failed to make use of it, had they been legally authorized to do so. Could the defendants, who as directors issued a prospectus stating that they had such power, be heard to deny, subsequently, that their statement was correct? Would they not be estopped? If so, then allegations by the plaintiff of the defendants' statement, whether accurate or not, and whether made in good faith or not, and of his own reliance upon it, would be sufficient basis for a judgment in his favor.