A systematist who would fit the living body of the law to his logical analytical scheme must proceed after the manner of Procrustes. Indeed, this is true of all science. In life phenomena are unique. The biologist of today sometimes doubts whether there are species and disclaims higher groups as more than conveniences of study. "Dividing lines," said a great American naturalist, "do not occur in nature except as accidents." Organization and system are logical constructions of the expounder rather than in the external world expounded. They are the means whereby we make our experience of that world intelligible and available. It is with no illusion, therefore, that I am leading you to a juristic _ultima Thule_ that I essay a bit of systematic legal science on a philosophical basis. Even if it never attains a final system in which the law shall stand fast forever, the continual juristic search for the more inclusive order, the continual juristic struggle for a simpler system that will better order and better reconcile the phenomena of the actual administration of justice, is no vain quest. Attempts to understand and to expound legal phenomena lead to generalizations which profoundly affect those phenomena, and criticism of those generalizations, in the light of the phenomena they seek to explain and to which they give rise, enables us to replace them or modify them or supplement them and thus to keep the law a growing instrument for achieving expanding human desires. One of the stock questions of the science of law is the nature and system and philosophical basis of situations in which one may exact from another that he "give or do or furnish something" (to use the Roman formula) for the advantage of the former. The classical Roman lawyer, thinking in terms of natural law, spoke of a bond or relation of right and law between them whereby the one might justly and legally exact and the other was bound in justice and law to perform. In modern times, thinking, whether he knows it or not, in terms of natural rights and by derivation of legal rights, the analytical jurist speaks of rights _in personam_. The Anglo-American lawyer, thinking in terms of procedure, speaks of contracts and torts, using the former term in a wide sense. If pressed, he may refer certain enforceable claims to exact and duties of answering to the exaction to a Romanist category of quasi-contract, satisfied to say "quasi" because on analysis they do not comport with his theory of contract, and to say "contract" because procedurally they are enforced _ex contractu_. Pressed further, he may be willing to add "quasi tort" for cases of common-law liability without fault and workmen's compensation--"quasi" because there is no fault, "tort" because procedurally the liability is given effect _ex delicto_. But cases of duties enforceable either _ex contractu_ or _ex delicto_ at the option of the pleader and cases where the most astute pleader is hard pushed