When a client asks his lawyer what his duties are under a particular contract, normally the lawyer’s first response is “show me the contract.” Does the contract provide all the contract duties in its expressed form? Definitely not. By now everyone acknowledges that, to some extent, all contracts have some gaps. Even the most carefully drafted document rests on volumes of assumptions that cannot be explicitly expressed.1 The inevitability of gaps reflects both our “relative ignorance of fact” and “our relative indeterminacy of aim.” Generally speaking, there are three types of gaps: first, the parties to a contract have not agreed upon a term; second, the parties have agreed upon a term, but the term itself is so vague that it is impossible to ascertain its meaning; and third, the parties have agreed to agree upon a term sometime after contract formation, but then never reach an agreement on that point. A remarkable trend in modern contract law is the relaxation of the requirement of certainty of terms. Modern legislation and courts are willing to enforce contracts even where many terms are missing, including such seemingly essential terms as time of delivery and price. But once the courts relax the certainty requirement, they themselves must find a way to fill the gaps in the binding arrangements.
Lu, Shumei, "Gap-filling and Freedom of Contract" (2000). LLM Theses and Essays. 29.