Why “must return” does not mean “returned”

In a program the result of a computation is a value. In law the result of applying a norm is most often not a fact but a position: someone is now under a duty, someone is at liberty, someone may change another’s position by their own act. A duty exists separately from whether it has been performed; a power exists separately from whether it has been exercised. This article explains why the language distinguishes facts and positions, and what would be lost if it reduced everything to the former.

Duty as a result

A researcher received a document to take home from 1 through 31 March. Norm: the recipient must return the document by the deadline. Ask the machine not “has the document been returned” but “in what state is the duty to return,” on different dates.

Date of the question	What is known beyond the issue	Duty to return
15 February	—	not yet arisen
15 March	—	active
15 March	document returned	satisfied
10 April	—	established as neither satisfied nor violated
10 April	non-return recorded by control	violated
10 April	issue extended	the ground is removed

Each row is a scene from the tutorial on duty, which the engine executes on every check. A program with facts would give one field “returned: yes/no.” Here the duty has a life of its own: it arises from the fact of issue, lives in the window of the deadline, and ends in one of several ways, and each way is a separate status with separate consequences.

The fourth row is the main one. The deadline has passed, nothing is known about the return, and the answer is not “violated.” Violation is not derived from silence: absence of proof of performance is not proof of non-performance. To get “violated,” the case must have an established fact of non-return, and here an act of control supplies it. Legally that is how it should be: non-return is established by a check, not by the calendar. A program that after the deadline has returned == false would have committed a substitution nobody would have noticed.

Duty, prohibition, liberty, power

There are four kinds of position, and the distinction among them is not classification for classification’s sake. Each has its own logic of existence.

Duty has a bearer, a goal, and a window. The goal comes in two kinds: reach a result by a deadline, or hold a state throughout the term. The second kind is violated by one counterexample and cannot be recognised as satisfied by one fact: to say “observed the whole term” needs completeness of observation for the whole term. The asymmetry here is the same as in law.

Prohibition is sugar over a duty of forbearance, and it has a property that surprises everyone: by itself it is not violated. The fact of a prohibited action makes the prohibition “active,” not “violated.” Violation is expressed by a paired duty, and that is not a defect: a prohibition in an act is still needed for two other things — for weak permission of everything else, and for conflict with a liberty to do the same action.

Liberty is a permission that may or may not be used. It has neither “satisfied” nor “violated,” only a window in which it is active. To ask “may Ivanova request an extension” is to ask the state of a liberty, not the truth of a fact.

Power is the authority to change another’s position by one’s own act. It fires in two steps: a rule creates the power, and the effect arrives only when both exercise (the director issued an order) and ground (an act of damage) are established. An order without a ground yields not an effect but a mark in the answer document: the power was exercised invalidly. A ground without an order is simply silence. These scenes are executed in the tutorial on modalities.

What a position gives the author

Three things a fact does not have.

• A state instead of a value. The same duty on different dates answers differently, and the answer says what to do: wait, demand, establish a fact, recognise it as removed.
• A life cycle with bounds. The window of a duty is computed from the facts of the case or from a calendar deadline; outside the window the answer differs from inside, and that is visible.
• A consequence is a separate norm. A penalty for delay is not a field of the duty but another norm that reads the same established facts. So violation, liability, and sanction remain different layers, and relief from the penalty cancels neither the fact of violation nor the qualification.

The price: the author must distinguish what exactly they are recording — a fact, a duty, a prohibition, a liberty, or a power — and name the required parts of each: bearer, goal, window, event of exercise, ground. The compiler refuses a missing part, and does so before execution.

What the language does not do here

It does not derive a violation from an expired deadline. It does not read a prohibition as a violation. It does not materialize the effect of a power without a ground. It does not choose between a valid power and an immunity from it until the author has declared which is senior. Each of these “does not” is a place where a program with facts would have made a choice silently, and here a human makes it and records it.

Next

The last article of the introduction is about what must be kept so that an answer can be repeated: the source, the legal date, the reading, the inputs, and why there are two checks. How positions are written — the tutorial on duty and the tutorial on modalities.