n, if in--

"'yonder sky,
My faithful dog should bear me company.'

"You are too familiar with the works of that Titan in wisdom and error,
Descartes, not to recollect the interesting correspondence between the
urbane philosopher and our combative countryman, Henry More,(3) on this
very subject; in which certainly More has the best of it when Descartes
insists on reducing what he calls the soul (l'ame) of brutes into the
same kind of machines as man constructs from inorganized matter. The
learning, indeed, lavished on the insoluble question involved in
the psychology of the inferior animals is a proof at least of the
all-inquisitive, redundant spirit of man.(4) We have almost a literature
in itself devoted to endeavours to interpret the language of brutes.(5)
Dupont de Nemours has discovered that dogs talk in vowels, using only
two consonants, G, Z, when they are angry. He asserts that cats
employ the same vowels as dogs; but their language is more affluent in
consonants, including M, N, B, R, V, F. How many laborious efforts have
been made to define and to construe the song of the nightingale! One
version of that song, by Beckstein, the naturalist, published in 1840,
I remember to have seen. And I heard a lady, gifted with a singularly
charming voice, chant the mysterious vowels with so exquisite a pathos,
that one could not refuse to believe her when she declared that she
fully comprehended the bird's meaning, and gave to the nightingale's
warble the tender interpretation of her own woman's heart.

"But leaving all such discussions to their proper place amongst the
Curiosities of Literature, I come in earnest to the question you have
so earnestly raised; and to me the distinction between man and the
lower animals in reference to a spiritual nature designed for a future
existence, and the mental operations whose uses are bounded to an
existence on earth, seems ineffaceably clear. Whether ideas or even
perceptions be innate or all formed by experience is a speculation
for metaphysicians, which, so far as it affects the question of as
immaterial principle, I am quite willing to lay aside. I can well
understand that a materialist may admit innate ideas in Man, as he
must admit them in the instinct of brutes, tracing them to hereditary
predispositions. On the other hand, we know that the most devout
believers in our spiritual nature have insisted, with Locke, in denying
any idea, even of the Deity, to be innate.