One who attempts to write on any topic of the law is likely to realize that what Maitland said of the historian is also true of the law writer, he is tearing a seamless web. The law cannot be divided into parts marked by exact boundaries, and the problem of where to stop continually confronts him. But however vague may be the boundaries of contract, it fills so larg a space in the law that the most formidable obstacle presented to one who chooses the subject is its magnitude. Included within it are large portions of what is contained in works on Vendor and Purchaser, Sales of Personal Property, Negotiable Instruments, Agency, Bailments, Carriers, Landlord and Tenant, Insurance, Suretyship, Equity, Master and Servant, Quasi-Contract, Damages, Evidence.

In view of this it might be thought the part of wisdom to be content to work within smaller compass; but the law of contracts suffers from a difficulty opposite to that which has hampered the development of the law of torts. That law grew up piecemeal and with limitations varying in different forms of action. Only in recent years has much effort been made to knit together with broad fundamental principles the various kinds of torts. The law of contracts, on the other hand, after starting with some degree of unity now tends from its very size to fall apart. The simplest applications of fundamental principles of contracts when found in an insurance policy or a contract of suretyship are often considered by writers on those topics as peculiarities of the law of insurance or of suretyship, controlled by no general rules. It therefore seems desirable to treat the subject of contracts as a whole, and to show the wide range of application of its principles.

I make no apology for devoting some space to legal analysis and criticism. Coke speaks of himself as "knowing for certain that the law is unknowen to him that knoweth not the reason thereof;" and in the modern welter of decisions on both sides of many questions, the learned Chief Justice would not be likely to change his mind were his lot cast in the twentieth century. But I have endeavored to keep my discussions within the limits of practical usefulness, and to make my statements of actual decisions as exact as possible.

It is as inevitable in law as in physical science that a writer must build upon the work of those who precede him. My indebtedness to past and present colleagues and to other writers is large, but of too general and varied character for particular prefatory acknowledgment.

In a work so comprehensive as that which I have undertaken, I cannot hope altogether to have escaped mistakes. I shall be grateful to any readers who, on finding me in error, will let me know of their discoveries.

SAMUEL WILLISTON. Cambridge, Mass. January, 1920.