But it is one thing to find legislative authority for applying the law as between subject and subject to a cause concerning the rights and obligations of governments; it is another thing to say how and with what effect the principles of that law do apply in substance. For the subject matters of private and public law are necessarily different. What is in question here is an agreement assuming to affect matters which are governmental and by nature are subject to considerations to which private law is not directed. That is particularly true of financial provisions, the fulfilment of which in constitutional theory at least must be subject to parliamentary control. All this was plainly seen by the late Sir Harrison Moore whose two papers, one posthumously published, on the questions involved will be found under the titles: " Suits between Commonwealth and State and State and State ", Journal of Comparative Legislation, (1925) 3rd Series, vol. 7 Pt IX), p. 155; " The Federation and Suits between Governments ". Journal of Comparative Legislation (1935) 3rd Series, vol. 17 (Pt IV), p. 163. From the later paper the Solicitor-General quoted the following passage which touches the very point here. "The High Court of Australia has more than once affirmed the rights and obligations subsisting between individuals as the guide to the ascertainment of the legal rights of which the Court has cognizance. That principle includes agreement as a category of right, but it would exclude agreements of which the subject of the mutual undertakings is the exercise of political power: the agreements are not such as are capable of existing between individuals, their subject-matter is the peculiar and exclusive characteristic of governments. Even an agreement of the Crown with an individual respecting the future exercise of discretionary powers - that they will or will not be exercised in a certain way - probably cannot be a valid contract." The learned author then gives examples of subjects inappropriate for agreements that could be judicially enforced and proceeds: - "The task of distinguishing the classes of agreement may not in all cases be easy, particularly in "mixed" agreements some of whose terms present one feature and some another. It is even possible that it may extend to exclude agreements in which every item could be conceived of as an agreement between individuals, but which were so comprehensive and far-reaching that on the whole they must be treated as removed from the category of individual or corporate agreements." In the present case we are concerned with an agreement which on both sides has the sanction of statute. Behind it there is a history of government agreements and attempted agreements affecting the same general subject with which this one deals. Some have been fulfilled. The agreement now in question certainly contains provisions which no court could undertake specifically to enforce, that is by detailed specific relief, yet in general terms what each government undertakes to do is defined or described with sufficient clearness, and, in the case of some provisions, on fulfilment of the work undertaken on one side there can be little doubt that the financial responsibilities on the other side would be considered legal obligations capable of enforcement by any judicial remedy available in the case of a government liability. Enough has been said to show that in the first place, to generalize about the operation of the agreement in question must be unsafe and misleading and that in the second place, it could only be in respect of some definite obligation the breach of which is unmistakably identified that a court can pronounce a judicial decree in a case such as this. It is only in this way that the necessary distinction can be maintained between, on the one hand, the exercise of the jurisdiction reposed in the Court and, on the other hand, an extension of the Court's true function into a domain that does not belong to it, namely, the consideration of undertakings and obligations depending entirely on political sanctions. The proceeding now before the Court, as already has been said, is a demurrer by the defendant to a statement of claim. All that such a demurrer does is to deny the legal sufficiency of the facts alleged in the pleading, that is, the sufficiency to entitle the plaintiff to a legal remedy. At common law, at the time when the system of common law pleading closed in England, a general demurrer to a count in a declaration formed an apt and almost certain way of ascertaining whether a cause of action was disclosed by the facts stated by the count. But it was necessary that they should be ultimate and not evidentiary facts. In equity a demurrer to a bill might have been on any of several grounds but that which would have been material in this case is that the allegations disclosed no equity to any of the relief prayed. In this Court the procedure of demurrer has been retained but a narrative and not a common law system of pleading has been adopted. There are certain difficulties now in the practical working of demurrers chiefly because the allegations in a pleading which are pointed at each specific or particular cause of action or ground of defence are not confined within a single definite count or plea. Further, the rules of pleading do not confine a plaintiff to the relief he had specifically claimed (21, 4) and this sometimes is a source of embarrassment in deciding a demurrer. Perhaps the reluctance of a party to amend pending a demurrer because of the rule as to costs should not be left out of account (26, 15). But the use of a demurrer, which certainly has been found a speedy and not unsatisfactory procedure in this Court, where causes depending on questions of ultra vires and upon other federal questions of statutory instruments are frequent, presupposes a pleading which is drawn so as to allege with distinctness and clearness the constituent facts of the cause of action or defence set up and which puts aside the temptation to adorn the pleading with evidentiary statements and tendentious legal conclusions. It is not going too far to say that what justifies demurrer as a means of determining a legal controversy is the supposition that the pleading will contain and contain only a statement of the material facts on which the party pleading relies for his claim or defence and not the evidence by which they are to be proved. (cf. 20, 4 (1)). When a court deals with a demurrer it should in strictness discard all statements which are no more than evidentiary and all statements involving some legal conclusion. It will be necessary to return to these principles when we reach the final question of what cause of action, if any, is disclosed by the pleading. But before that point is reached the character of the agreement put in suit must be described.