Full Idea
'Strict' laws of nature contain no ceteris paribus clauses ('all things being equal'), and are part of a closed system (so that whatever affects the system must be included within the system).
Gist of Idea
Strict laws allow no exceptions and are part of a closed system
Source
Keith T. Maslin (Introduction to the Philosophy of Mind [2001], 7.5)
Book Reference
Maslin,Keith: 'An Introduction to the Philosophy of Mind' [Polity 2001], p.201