e already _knows_ even to repletion?

It is not its importance, then, which confers upon truth its value in
communication. In other words, it is a most superfluous civility for one
man to impart truth to another, solely because it happens to be
important. If the important truth be already perfectly well known to the
recipient, and if the imparter of it is aware that the recipient knows
it just as well as he does,--"thank you _for nothing_" is, we think, the
mildest reply that could be made in the circumstances. The fact is, that
the value of truth is measured by precisely the same standard which
determines the value of wealth. This standard is in neither case the
importance of the article,--it is always its difficulty of
attainment,--its cost of production. Has _labour_ been expended on its
formation or acquisition; then the article, if a material commodity, has
a value in exchange--if a truth, it has a value in communication. Has no
labour been bestowed upon it, and has Nature herself furnished it to
every human being in overflowing abundance, then the thing is altogether
destitute of exchange-value--whether it be an article of matter or of
mind. No man can, without impertinence, transmit or convey such a
commodity to his neighbour.

If this be the law on the subject, (and we conceive that it must be so
ruled) it settles the question as to the _second_ mode of dealing with
the problem of perception. It establishes the point that this method of
treating the problem is not to be permitted. It is _tabooed_ by the very
nature of things. Air and sunshine are excellent and most important
articles, but they are not things to carry to market in
bottles,--because no labour is required to produce them, and because
they are the gratuitous and abundant property of every living soul. In
the same way, the existence of a material universe--and the fact that
we believe in its existence--these are most important truths; but they
are not things to take to market in books, and for a like reason. They
are important things to _know_, but they are not important things to
_tell_. We conceive, in short, that Nature, by rendering these and
similar truths unreservedly patent to the whole human race, has affixed
to them her own contraband,--interdicting their communication; and that
Dr Reid, in making them the staple of his publications, was fighting
against an eternal law. He undertook to teach the world certain truths
connected with perceptio