A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. II
John Stuart Mill · en
Descartes, in like manner, whose works are a rich mine of almost every
description of _à priori_ fallacy, says that the Efficient Cause must at
least have all the perfections of the effect, and for this singular
reason: "Si enim ponamus aliquid in ideâ reperiri quod non fuerit in
ejus causâ, hoc igitur habet a nihilo;" of which it is scarcely a parody
to say, that if there be pepper in the soup there must be pepper in the
cook who made it, since otherwise the pepper would be without a cause. A
similar fallacy is committed by Cicero in his second book _De Finibus_,
where, speaking in his own person against the Epicureans, he charges
them with inconsistency in saying that the pleasures of the mind had
their origin from those of the body, and yet that the former were more
valuable, as if the effect could surpass the cause. "Animi voluptas
oritur propter voluptatem corporis, et major est animi voluptas quam
corporis? ita fit ut gratulator lætior sit quam is cui gratulatur." Even
that, surely, is not an impossibility: a person's good fortune has often
given more pleasure to others than it gave to the person himself.
Descartes, with no less readiness, applies the same principle the
converse way, and infers the nature of the effects from the assumption
that they must, in this or that property or in all their properties,
resemble their cause. To this class belong his speculations, and those
of so many others after him, tending to infer the order of the universe,
not from observation, but by _à priori_ reasoning from supposed
qualities of the Godhead. This sort of inference was probably never
carried to a greater length than it was in one particular instance by
Descartes, when, as a proof of one of his physical principles, that the
quantity of motion in the universe is invariable, he had recourse to the
immutability of the Divine Nature. Reasoning of a very similar character
is however nearly as common now as it was in his time, and does duty
largely as a means of fencing off disagreeable conclusions. Writers have
not yet ceased to oppose the theory of divine benevolence to the
evidence of physical facts, to the principle of population for example.
And people seem in general to think that they have used a very powerful
argument, when they have said, that to suppose some proposition true,
would be a reflection on the goodness or wisdom of the Deity. Put into
the simplest possible terms, their argument is, "If it had depended on
me, I would not have made the proposition true, therefore it is not
true." Put into other words it stands thus: "God is perfect, therefore
(what I think) perfection must obtain in nature." But since in reality
every one feels that nature is very far from perfect, the doctrine is
never applied consistently. It furnishes an argument which (like many
others of a similar character) people like to appeal to when it makes
for their own side. Nobody is convinced by it, but each appears to think