Determinism Is a Legal Requirement

A decision that cannot be reproduced cannot be defended.

Law does not tolerate probability. Law requires certainty.

I. The Difference Between Engineering and Law

Engineering tolerates approximation:

retries

heuristics

best-effort outcomes

Law does not.

A system may function under uncertainty. A legal system may not.

If the same inputs do not produce the same outcome, the system is unlawful.

II. Non-Determinism Destroys Accountability

Non-deterministic systems:

cannot explain outcomes

cannot justify decisions

cannot resolve disputes

When an auditor asks:

“Why did this happen?”

“Because the system behaved differently” is not an answer.

It is an admission of failure.

III. Time, Order, and Hidden Inputs

Determinism fails when execution depends on:

wall-clock time

race conditions

concurrency ordering

random seeds

external services

If any of these affect outcome, replay is impossible.

Without replay, audit collapses.

IV. Idempotency Is Not Determinism

Idempotency ensures safety under repetition. It does not ensure equality of result.

A system can be idempotent and still non-deterministic.

Law requires sameness, not merely harmlessness.

V. Determinism Requires Closed Worlds

A deterministic system:

controls all inputs

versions all rules

isolates execution

freezes dependencies

Anything externalized:

APIs

configurations

mutable schemas

introduces uncertainty.

Uncertainty is inadmissible.

VI. Determinism Enables Proof

Determinism allows a system to state:

“Given these inputs, under this law, this outcome was inevitable.”

That statement is proof.

Without determinism, there is only narrative.

Narrative is not evidence.

VII. Legal Systems Are Deterministic by Definition

Courts do not accept:

“it usually works”

“it depends”

“the system decided”

They accept:

causality

inevitability

reproducibility

Any system participating in legal reality must satisfy the same standard.

VIII. Final Conclusion

Determinism is not an optimization. It is a legal requirement.

A lawful system:

produces the same result for the same inputs

records the law applied

allows full replay at any time

Anything else is computational chance masquerading as governance.