"The laws of chemistry and physiology (for example) owe their existence to a breach of the principle of composition of causes, but these heteropathic laws, as we might call them, are capable of composition with one another. The causes which by one combination had their laws altered may carry their new laws with them unaltered into further combinations. So we needn’t despair of eventually raising chemistry and physiology to the condition of deductive sciences; for though it’s impossible to deduce all chemical and physiological truths from the laws or properties of simple substances or elementary agents, perhaps they are deducible from laws that come into play when these elementary agents are brought together into some moderate number of not very complex combinations. The laws of life will never be deducible from the mere laws of the ingredients, but the prodigiously complex facts of life may all be deducible from comparatively simple laws of life—which do indeed depend on combinations, but comparatively simple ones."