Main idea

A finished document contains two things mixed together: what is true of the subject, and what was decided for that particular audience. The tone, the level of detail, the order, the degree of caution, the way things are named, what you reveal and what you assume already known — none of that belongs to the knowledge itself.

Starting again from that document to produce the next one therefore means inheriting those choices without having chosen them. A sentence written to reassure a client becomes the basis of internal documentation; a slide formulation becomes a specification requirement.

The defect isn't producing several documents. It is taking an output as a source.

Layer added by "Code Centric" (2026-04-13). The rule applies to a software product chain too, where it is almost always broken without anyone noticing: updating a specification means reopening the previous version and correcting the paragraphs affected, which is to say taking an output as a source. The document then inherits everything that wasn't reread — screens removed since, assumptions disproved during development. This case has a useful peculiarity: the non-oriented source is identifiable beyond dispute, it is the code repository, and you can therefore measure what the inheritance costs rather than assume it.

Layer added by "Information systems aren't going away. Their shape is changing." (2026-07-08). What the rule asks you to accept is costlier than it looks, and that is what makes it fail in organizations rather than in methods: accepting that a document handed over is an output and not the source amounts to stripping the deliverable of its status as proof of work done. As long as that is what you are judged on, starting from elsewhere means maintaining material nobody looks at.

Why it matters

This is the mechanism by which two versions of the same truth end up diverging. Every copy rephrases, removes what doesn't speak to the new audience, adds what is missing — and loses along the way a nuance nobody sees disappear, since it is only absent from the new document.

The consequence is operational: support may explain something other than sales does, and the specification may carry an assumption absent from the leadership story, with no control detecting it.

Nuances and limits

The inheritance is sometimes deliberate: taking up a client's vocabulary in a document meant for that same client is a good decision, not contamination.

And a neutral source guarantees nothing on its own — each output still has to be genuinely remade from it rather than from the previous one.

Open questions

• How do you detect a divergence between two documents that each, taken alone, look correct?