Definition
"Is to" is a phrase of legal construction that, when appearing in a document, instrument, or statute, expresses an analogical or proportional relationship between terms — most commonly encountered in the form "A is to B as C is to D." In legal usage, the phrase also functions as a term of obligation or futurity, conveying that something shall be done or is required to occur, distinct from a present-state declaration. Courts have occasionally been called upon to construe the phrase when its meaning in context is ambiguous between a descriptive statement (describing what something is) and a prescriptive or obligatory one (describing what something ought to be or must become).
Common Confusion
Researchers occasionally conflate the construction of "is to" as a term of futurity or obligation with the grammatical copula "is" standing alone. The distinction matters: "is" in a statute or instrument typically describes present condition or classification, while "is to" carries an element of prospective requirement or purpose. Courts have treated the difference as potentially determinative when construing whether a legislative or contractual provision is mandatory or merely descriptive. Do not assume that historical cases construing "is" resolve questions about "is to," or vice versa.
Why It Matters in Research
This term appears in Rapalje & Lawrence under a cluster of entries devoted to the judicial construction of specific words and phrases — a feature of nineteenth-century legal dictionaries reflecting the era's heavy reliance on reported decisions interpreting particular language. Researchers working in historical sources should understand that these phrase-construction entries are not definitions of legal concepts but rather digests of interpretive rulings: courts said what a phrase meant in a specific document, and the lexicographers collected those rulings as guides.
The practical trap for Law Mind corpus researchers is one of miscategorization. "Is to" may appear in a historical index or digest as a standalone entry, but the surrounding entries (THAT SAY, THAT WHEREAS, THE, THE BALANCE OF CASH) reveal the organizing principle: these are words-and-phrases entries, not doctrinal concepts. When researching historical construction of contract, statutory, or indictment language, look for this type of entry not in the conceptual index but in the words-and-phrases sections of nineteenth-century digests and in dedicated compilations such as Words and Phrases (West).
Researchers should also note the temporal dimension. The obligatory reading of "is to" — meaning "shall" or "must" — was more frequently litigated in nineteenth-century instruments, where drafting precision was inconsistent and courts regularly faced the question of whether language was directory or mandatory. Modern drafting conventions generally substitute "shall," "must," or "will" for this construction, so the phrase arises more often in historical document analysis than in contemporary litigation.
Historical Dictionary Support
Rapalje & Lawrence do not provide a substantive entry for "is to" as a freestanding term. The phrase appears only in the source material's surrounding context, grouped with other words-and-phrases construction entries drawn from reported decisions. This is consistent with the methodology of that dictionary: rather than define abstract legal concepts, Rapalje & Lawrence catalogued how specific language had been judicially interpreted, citing particular cases as authority.
The absence of a developed entry is itself informative. It suggests the phrase did not generate sufficient independent litigation to warrant doctrinal treatment, appearing instead as a subsidiary construction question within contract, statutory, and pleading cases. Researchers consulting Rapalje & Lawrence for this phrase will find it less useful than a true words-and-phrases digest, which would collect the relevant cases by document type (contract, will, statute, indictment) and by the specific interpretive question raised.
Historical dictionaries generally — including Bouvier and Black's early editions — do not treat "is to" as a term of art. This is consistent with its character as a phrase whose legal significance is entirely context-dependent rather than definitionally fixed.