To find then what a corruption or perversion of the truth is, let us inquire what the word means, when used literally of material substances. Now it is plain, first of all, that a corruption is a word attaching to organized matters only; a stone may be crushed to powder, but it cannot be corrupted. Corruption, on the contrary, is the breaking up of life, preparatory to its termination. This resolution of a body into its component parts is the stage before its dissolution; it begins when life has reached its perfection, and it is the sequel, or rather the continuation, of that process towards perfection, being at the same time the reversal and undoing of what went before. Till this point of regression is reached, the body has a function of its own, and a direction and aim in its action, and a nature with laws; these it is now losing, and the traits and tokens of former years; and with them its vigour and powers of nutrition, of assimilation, and of self-reparation.

Taking this analogy as a guide, I venture to set down seven Notes of varying cogency, independence and applicability, to discriminate healthy developments of an idea from its state of corruption and decay, as follows:—There is no corruption if it retains one and the same type, the same principles, the same organization; if its beginnings anticipate its subsequent phases, and its later phenomena protect and subserve its earlier; if it has a power of assimilation and revival, and a vigorous action from first to last. On these tests I shall now enlarge, nearly in the order in which I have enumerated them. — from On the Development of Doctrine