Note 20 — Chapter IV

§ 30. All and every law follows as a necessary consequence from the persistence of force and the primary qualities of matter.[20] That this must be so is evident if we consider that, were it not so, force could not be permanent nor matter constant. For instance, if action and reaction were not invariably equal and opposite, force would not be invariably persistent, seeing that in no case can the formula fail, unless some one or other of the forces concerned, or parts of them, disappear. And as with a simple law of this kind, so with every other natural law and inter-operation of laws, howsoever complex such inter-operation may be; for it is manifest that if in any case similar antecedents did not determine similar consequents, on one or other of these occasions some quantum of force, or of matter, or of both, must have disappeared—or, which is the same thing, the law of causation cannot have been constant. Every natural law, therefore, may be defined as the formula of a sequence, which must either ensue upon certain forces of a given intensity impinging upon certain given quantities, kinds, and forms of matter, or else, by not ensuing, prove that the force or the matter concerned were not of a permanent nature.