A clear conception of the law governing assignment of contracts can only be obtained by sharply distinguishing between attempted assignments of rights and of liabilities. Where assignment of choses in action is spoken of, assignment of rights is properly to be understood; but as every bilateral contract involves not only rights but duties on each side, any attempted assignment of such a contract while both Bides are still executory, requires consideration of its effect on both rights and duties. The discussion of the subject has been much confused and is made intrinsically more difficult by the fact that the common words, contract, debt, obligation, are used to express both the right of the obligor and also the duty of the obligee. If specific attention is directed to whether it is a contractual right or a duty or both to which a proposed transfer relates, the gain to clearness of thought is considerable. The problem of assignment of contractual rights was earliest considered by the law, and is properly here first considered.

11 See infra, Sec.1135 et seq.

12 Purvis v. Shuman, 273 111. 286, 112 N. E. 679, 682. See also Wright v. Pfimmer, 99 Neb. 447,156 N. W. 1060,

L. R. A. 1917 A. 323; Korn v. Campbell, 192 N. Y. 490, 85 N. E. 687, 37 L. R. A. (N. S.) 1 (note on p. 12), 127 Am. St. 925, and notes thereto.