  Safety and assurance standards often rely on the principle that requirements
errors can be minimised by expressing the requirements more formally. Although
numerous case studies have shown that the act of formalising previously
informal requirements finds requirements errors, this principle is really just
a hypothesis. An industrially persuasive causal relationship between
formalisation and better requirements has yet to be established. We describe
multiple competing explanations for this hypothesis, in terms of the levels of
precision, re-formulation, expertise, effort and automation that are typically
associated with formalising requirements. We then propose an experiment to
distinguish between these explanations, without necessarily excluding the
possibility that none of them are correct.
