The Government of Western Australia publicly offered "a reward of £1,000 for such information as should lead to the arrest and conviction of the person or persons who murdered John Joseph Walsh, inspector of police, and Alexander Henry Pitman, sergeant of police." The petitioner knew of this offer and with that knowledge performed some at least of its conditions, but the learned Judge who tried the action - McMillan C.J. - found that he did not act on the faith of, or in reliance upon, the offer or with any intention of entering into any contract. Mutual assent or a consensus of wills is essential in English law to the formation of a contract. However, in the law of contract the offer of a reward addressed to the world at large stands in a somewhat anomalous position, and it is argued that the performance of the conditions of such an offer is an acceptance of it. This argument finds support in the case of Williams v. Carwardine[44]. The jury found in that case that the plaintiff was not induced by the offer of the reward to give the information required and yet the plaintiff had a verdict. But the case has been criticized and said to be an authority only for the proposition that the motive of compliance with an offer is immaterial (Anson on Contracts, 15th ed., p. 55), and Professor Langdell boldly says that it seems to have been erroneously decided (Cases on Contracts, 2nd ed. (1879), Summary, p. 988, par. 3; see also Pollock on Contract, 9th ed., p. 23; Benjamin on Sales, 7th ed., pp. 71, 72). And, indeed, if it does set up "a contract without any privity between the parties" it certainly runs counter to well settled principles of the English law of contract and must be disregarded. In Carlill v. Carbolic Smoke Ball Co.[45] it is said that the general offer of a reward is an offer made to any person who acts upon the faith of or in reliance upon that offer and performs the conditions specified in it. (Lindley L.J.[46], Bowen L.J.[47], A. L. Smith L.J.[48]). Such an offer is capable of acceptance by a number of persons but the person entitled to the reward depends upon the terms and nature of the offer (Lancaster v. Walsh[49]). And previous communication of its acceptance is not required (Carlill v. Carbolic Smoke Ball Co.). A number of other cases, both English and American, relevant to the matter in hand, might be cited; but I content myself with a reference to the collection made in the notes to Williams v. Carwardine[50] in Ruling Cases, vol. vi., Contract, pp. 133-139. In my opinion the true principle applicable to this type of case is that unless a person performs the conditions of the offer, acting upon its faith or in reliance upon it, he does not accept the offer and the offeror is not bound to him. As a matter of proof any person knowing of the offer who performs its conditions establishes prima facie an acceptance of that offer (see Langdell on Contracts, 2nd ed. (1879), Summary, p. 988, par. 3). And probably, as Professor Langdell suggests (ibid.), the performance of some of the conditions required by the offer also establishes prima facie an acceptance of that offer, but does not of course establish the right of the person so performing some of the conditions of the offer to the reward until he has completely performed them all according to the proper construction of the offer. From such facts an acceptance is probable but it is not, as was urged, "an absolute proposition of law" that one, who, having the offer before him, acts as one would naturally be induced to act, is deemed to have acted on the faith of or in reliance upon that offer. It is an inference of fact and may be excluded by evidence (cf. Pollock on Torts, 11th ed., p. 303). The statements or conduct of the party himself uncommunicated to the other party, or the circumstances of the case, may supply that evidence. Ordinarily, it is true, the law judges of the intention of a person in making a contract by outward expression only by words or acts communicated between them (cf. Leake on Contracts, 3rd ed., p. 2; Brogden v. Metropolitan Railway Co.[51]). But when the offeror, as in the anomalous case under consideration, has dispensed with any previous communication to himself of the acceptance of the offer the law is deprived of one of the means by which it judges of the intention of the parties, and the performance of the conditions of the offer is not in all cases conclusive for they may have been performed by one who never hears of the offer or who never intended to accept it. Hence the statements or conduct of the party himself uncommunicated to the other party are admissible to show the circumstances under which an act, seemingly within the terms of the offer, was done and the inducement which led to the act. In the present case the statements of the petitioner himself satisfied the Chief Justice that he did not act on the faith of or in reliance upon the offer and we are unable to disturb that finding. I should have had more hesitation than the learned Judge in displacing the inference open on the facts that the petitioner knew of the offer and did in fact supply the Crown with most valuable information. Nowhere in the evidence is it said that he did not act upon the faith of or in reliance upon the offer, and it is unfortunate that no direct question was put to him upon the matter. The petitioner's statements are, I think, consistent with the position that he acted upon the offer but had not addressed his mind to the question whether he would or would not claim the reward. However, the proper inference of fact is essentially one for the learned Judge who saw and heard the petitioner.