erected their
castles upon a basis far less reliable than air; _for no such things as
axioms ever existed or can possibly exist at all_. This they must have
been very blind, indeed, not to see, or at least to suspect; for, even
in their own day, many of their long-admitted 'axioms' had been
abandoned:--'_ex nihilo nihil fit_,' for example, and a 'thing cannot act
where it is not,' and 'there cannot be antipodes,' and 'darkness cannot
proceed from light.' These and numerous similar propositions formerly
accepted, without hesitation, as axioms, or undeniable truths, were,
even at the period of which I speak, seen to be altogether
untenable:--how absurd in these people, then, to persist in relying upon
a basis, as immutable, whose mutability had become so repeatedly
manifest!

"But, even through evidence afforded by themselves against themselves,
it is easy to convict these _a priori_ reasoners of the grossest
unreason--it is easy to show the futility--the impalpability of their
axioms in general. I have now lying before me"--it will be observed that
we still proceed with the letter--"I have now lying before me a book
printed about a thousand years ago. Pundit assures me that it is
decidedly the cleverest ancient work on its topic, which is 'Logic.' The
author, who was much esteemed in his day, was one Miller, or Mill; and
we find it recorded of him, as a point of some importance, that he rode
a mill-horse whom he called Jeremy Bentham:--but let us glance at the
volume itself!

"Ah!--'Ability or inability to conceive,' says Mr. Mill very properly,
'is _in no case_ to be received as a criterion of axiomatic truth.' Now,
that this is a palpable truism no one in his senses will deny. _Not_ to
admit the proposition, is to insinuate a charge of variability in Truth
itself, whose very title is a synonym of the Steadfast. If ability to
conceive be taken as a criterion of Truth, then a truth to _David_ Hume
would very seldom be a truth to _Joe_; and ninety-nine hundredths of
what is undeniable in Heaven would be demonstrable falsity upon Earth.
The proposition of Mr. Mill, then, is sustained. I will not grant it to
be an _axiom_; and this merely because I am showing that _no_ axioms
exist; but, with a distinction which could not have been cavilled at
even by Mr. Mill himself, I am ready to grant that, _if_ an axiom _there
be_, then the proposition of which we speak has the fullest right to be
considered an axiom--that no _more_