Contract Doctrine, Theory & Practice Volume 3, 2012a

meaning. Courts frustrate this goal when they permit contextual
evidence to undermine the comparative certainty of a writing.
Although these competing concerns apply equally to both identifying
and interpreting terms, the cases that follow focus on the problem of
identifying which terms will become part of a contract. The common
law parol evidence rule and UCC § 2-202 provide the legal
framework within which this issue is analyzed.
1 The Common Law Parol Evidence Rule
Courts use the common law parol evidence rule to decide whether a
party may try to prove contract terms beyond those contained in a
written agreement. The traditional textualist approach to this
question—the so-called “four corners test”—asked simply whether
the written contract appeared complete on its face. If so, both parties
would be barred from introducing evidence of any prior or
contemporaneous agreement about the same transaction.
Contemporary case law has embraced a far more permissive standard
that asks instead whether the alleged additional terms “would
naturally have been excluded” from the writing. See Restatement
(Second) of Contracts § 216. In the majority of US jurisdictions, the
common law thus has evolved from a relatively strict parol evidence
rule to a comparatively lax standard that is far more likely to permit
parties to offer evidence of informal agreements to vary the terms of
a writing.
Despite this evolution towards contextualism, constraints remain.
The modern parol evidence rule still limits proof of additional terms.
It is convenient to distinguish two stages of analysis. Courts ask first
whether the parties’ written agreement is partially or totally
“integrated” and then whether the proffered additional term is
“consistent” with the written terms.
The touchstone for integration is an inquiry into whether the parties
intended the writing to be a final and exclusive statement of their
agreement. The written contract is fully (or “completely”) integrated
if it was meant to exclude all prior or contemporaneous
understandings between the parties, and it is partially integrated if it is
the final statement of only some of the terms of their agreement. An
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