A borrowed pattern transfers only as far as source and target share a mechanism

Type: kb/types/note.md · Tags: foundations

A pattern developed in one domain can be adopted in another without a fresh justification only over the layer where the two domains share the mechanism that makes the pattern work. Where the correspondence is analogy rather than shared mechanism — or where a shared mechanism exists but does not reach the part of the target the pattern touches — the pattern carries no transferred warrant and must earn adoption through target-side evidence.

The discriminator is mechanism identity, not surface similarity. Two systems can look alike — both formal, both text-based, both compositional — while the specific feature a pattern depends on is present in one and absent in the other. Transfer is licensed exactly as far as the depended-on mechanism is actually shared, and no further. So the unit of transfer is not the source domain as a whole but the specific mechanism a specific pattern rests on: one source can license fast adoption for a pattern whose mechanism it shares and none for a pattern related only by analogy.

This bounds a common shortcut. "Domain X and domain Y are both Z, so X's practices transfer to Y" over-grants: being both Z transfers only the practices that depend on Z, and only into the parts of Y that are actually Z. A borrowed practice that leans on a mechanism the target lacks — even when the domains are broadly alike — is analogy wearing the costume of mechanism, and owes the same target-side evidence any untested import owes. The correction is to locate the shared mechanism precisely and license transfer only over its reach; past that boundary the pattern is a conjecture to be tested, not an inheritance.

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Relevant Notes:

• Source-adoption policy — evidenced-by: Commonplace applies this discriminator, giving programming patterns a fast pass only over the shared symbolic-artifact layer, not the LLM's interpretive core