This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Whether notice of the assignment must be given to the debtor in order to protect the rights of the assignee, is a question the answer to which is determined largely by the theory of the purpose for which notice is requisite. According to one theory, the only purpose of such notice is to protect the debtor. Under this theory notice of an assignment is necessary only in cases in which the debtor has paid the debt to the original creditor or to one who claims under him, without notice of the assignment in question.1 According to the other theory, the purpose of notice is to make the assignee who gives the notice the master of the chose in action, and to divest the title of the assignor in favor of the assignee.2 The practical difficulty in applying these two theories and distinguishing between them is due to the fact that while as a rule the courts which have adopted the first theory have applied it logically, the courts which have adopted the second theory have frequently shrunk from applying it, except for the purpose of protecting another bona fide assignee who takes for value and without notice. For this reason the courts which have apparently accepted the second theory, frequently reach results which apparently can be justified only by the first theory.
Nebraska. Williams v. Donnelly, 54 Neb. 193, 74 N. W. 601.
New York. Moore v. Bank, 55 N. Y. 41, 41 Am. Rep. 173 [overruling, Bush v. Lathrop, 22 N. Y. 535].
6 Y. M. C. A. Gymnasium Co. v. Bank, 179 111. 599, 70 Am. St. Rep. 135, 46 L. R. A. 753, 54 N. E. 207.
7 Moore v. Moore, 112 Ind. 149, 2 Am. St. Rep. 170, 13 N. E. 673.
8 Western Bank v. Bank, 90 On. 339, 35 Am. St. Rep. 210, 16 S. E. 942; Yarnell v. Brown, 170 111. 362, 62 Am. St. Rep. 380, 48 N. E. 909.
9 Yarnell v. Brown, 170 111. 362, 62 Am. St. Rep. 380, 48 N. E. 909.
10 Western Bank v. Bank, 90 Ga. 339, 35 Am. St. Rep. 210, 16 S. E. 942.
1 England. Unwin v. Grosvenor, West Ch. 647.
United States. Knickerbocker Trust Co. v. Coyle, 139 Fed. 792.
Massachusetts. Hellen v. Boston, 194 Mass. 579, 80 N. E. 603.
North Carolina. Virginia-Carolina Chemical Co. v. McNair, 139 N. Car. 326. 51 S. E. 949.
Washington. Dial v. Inland Logging Co.. 52 Wash. 81, 100 Pac. 157.
On the subject of notice, see Notice of Assignments in Equity, by Edward Q. Keasbey, 19 Yale Law Journal, 258.