How 'Must' Became Law

We usually look to statutes and formal rules to find the limits on what we can do, but many of the limits we meet every day come through grammar, with no announcement. Tiny, everyday verbs like must, should, may, ought, have to, and need to quietly carry authority. They rarely sound like commands, yet they mark out what is required, what is permitted, and what is off-limits. These words are powerful because they work best when unnoticed, slipping obligation into a sentence as if it were an immutable part of reality. They seldom name who made the rule and conveniently omit the penalty for its violation.

That makes them useful to anyone writing rules who wants people to comply without arguing. We find them in the dense boilerplate of contracts and HR manuals, but also in the moral syntax of sermons, the hierarchical lessons of colonial textbooks, and the frictionless agreements of app terms of service.

Tracing how these verbs came to carry orders shows how a rule can bind people while its author stays out of sight.

The move is easiest to see in an invented pair. A rule can name whoever gives it:

“The king commands every tenant to deliver grain.”

Or it can leave that person out:

“Every tenant shall deliver grain at Michaelmas.”

Real law made the move, though the king never quite left. In 1349, in the middle of the Black Death, Edward III issued an ordinance on labourers. The king speaks in the first person at the top, where he has “seen fit to ordain.” The obligation itself is in the third person: every man and woman “of whatever condition, whether bond or free, who is able bodied and below the age of sixty years,” if sought for suitable work, “shall be bound to serve him who has seen fit so to seek after him.” Anyone who refused “shall be taken and sent to the next jail.”1

Acts of Parliament still name the sovereign. One passed in January 2024 opens: “Be it enacted by the King’s most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as follows.”2 The author didn’t vanish. He moved into an opening formula nobody reads, and shall, must and may carry his authority through every clause below it. An HR manual drops even the formula, and the first critical question to ask of one is who, exactly, benefits from leaving the decision-maker’s name out.

This external command soon found an internal counterpart. The word ought began its life as a simple synonym for owe. English Bibles record the turn. In the Wycliffe translation of the late 1300s, a debtor in Luke 7:41 “auyt fyue hundrid pans,” while in Luke 18:1 the duty to pray is carried by another word: “it bihoueth to preye euer more.” By Tyndale’s version of 1534, ought does both jobs. The debtor “ought five hondred pence,” and “men ought alwayes to praye.” The King James Bible kept both in 1611; its 1769 revision changed the debtor’s ought to owed and left the praying alone.3 The money went out of the word and the obligation stayed, with no creditor attached: you ought to pray; you ought to obey.

By the time the factory era dawned, this internalized command was fully formed. A worker ought to arrive early and never complain—no overseer needed to be present for the rule to be felt. When we hear ought today, we’re hearing the echo of this history; the expectation we’re still shouldering has a lineage, and tracing it pays.

The bare command has been losing ground for decades. Between the 1960s and the 1990s, must fell by 29 percent in written British English and by 54 percent in speech, and the linguist reporting the figures gives a likely reason: speakers “have become less willing to impose obligations on others.”4 Workplaces still impose them. They phrase them as facts:

“Employees have to clock in by six.” “You need to fill out this form.”

The language presents the rule as a precondition for reality to proceed as scheduled rather than an order from a person. It sounds like a simple statement of fact, but the penalty for ignoring it—job loss, a denied claim—is entirely real. This tone was perfectly suited to the logic of the punch-clock and the assembly line: a system of steady, pervasive control presented as the normal state of affairs. When a “fact” functions to control behavior, we should treat it as a rule and try to trace its source.

Grammar books taught the same ladder wherever English was taught: must for a command, should for firm advice, may for permission granted from above. Taught as usage, it was also a lesson in who gets to command whom.

The urge to codify authority reached logic in the mid-20th century, when philosophers of logic attempted to translate these messy concepts into formal symbols.

Georg Henrik von Wright, a pioneer in this field of “deontic logic,” proposed a system of operators for “it is obligatory that” and “it is permitted that,” modeled on the □ and ◇ of the logic of necessity and possibility. But real life, with its clashing rules and contextual nuances, quickly broke the model.

Ross’s paradox, from 1941, showed the problem. If you accept the rule “You ought to mail the letter,” logic dictates that you must also accept “You ought to mail the letter or burn it”—a permission that the original rule-giver certainly didn’t intend. In practice no one reads the rule that way. Readers work out what the person behind it wanted, which means an obligation can’t be read off the sentence alone: it needs the author the sentence left out. When the author is missing, whoever enforces the rule decides what it meant.

Nowhere is this truer than in the digital architecture of the checkbox. Nearly every app’s Terms of Service includes a variation of the line:

“Users must comply with all applicable laws.”

The single word must delegates sweeping interpretive power to the platform. Which laws? Who’s the arbiter of compliance? With one click on a box labeled “I agree,” a modal verb replaces the deliberation of a courtroom. It’s the shall move taken further, with authority that has no named source, takes effect instantly, and is accepted without argument.

Before clicking, it’s wise to scan for must, shall, or the tell-tale phrase “we reserve the right.” Enforcement hides in that phrase.

But none of this is immutable. These instruments of power were constructed, taught, and normalized, which means they can be deconstructed, questioned, and re-evaluated. The first step is to cultivate a new kind of literacy—to read with our eyes open to these subtle coercions.

• We can put the people back into the sentence, transforming “Equipment shall be returned” into the more honest “Supervisors require staff to return equipment.”
• We can ask for the source of a policy and who has the power to change it.
• We can reserve hard modals like must for true non-negotiables, like safety, and use gentler terms for routine requests.

Reading the verbs closely shows who left their name out of a rule, even while the rule stays in force. Once we know that, we can ask the question an agentless rule never answers:

Says who?

Sometimes, that’s the beginning of a better answer.