The Mind and the Brain | Page 5

course of his labours; to those sensations are added
the very numerous interpretations derived from the memory, reasoning,
and often, also, from the imagination on the part of the scholar, the last
a source at once of errors and of discoveries. But everything properly
experimental in the work of the zoologist proceeds from the sensations
he has felt or might have felt, and in the particular case treated of, these
sensations are almost solely visual.
This observation might be repeated with regard to all objects of the
outer world which enter into relation with us. Whether the knowledge
of them be of the common-place or of a scientific order matters little.
Sensation is its limit, and all objects are known to us by the sensations
they produce in us, and are known to us solely in this manner. A
landscape is nothing but a cluster of sensations. The outward form of a
body is simply sensation; and the innermost and most delicate material
structure, the last visible elements of a cell, for example, are all, in so
far as we observe them with the microscope, nothing but sensation.
This being understood, the question is, why we have just
admitted--with the majority of authors--that we cannot really know a
single object as it is in itself, and in its own nature, otherwise than by

the intermediary of the sensations it provokes in us? This comes back
to saying that we here require explanations on the two following points:
why do we admit that we do not really perceive the objects, but only
something intermediate between them and us; and why do we call this
something intermediate a sensation? On this second point I will offer,
for the time being, one simple remark: we use the term sensation for
lack of any other to express the intermediate character of our perception
of objects; and this use does not, on our part, imply any hypothesis.
Especially do we leave completely in suspense the question whether
sensation is a material phenomenon or a state of being of the mind.
These are questions we will deal with later. For the present it must be
understood that the word sensation is simply a term for the something
intermediate between the object and our faculty of cognition.[3] We
have, therefore, simply to state why we have admitted that the external
perception of objects is produced mediately or by procuration.
There are a few philosophers, and those not of the lowest rank, who
have thought that this intermediate character of all perception was so
evident that there was no need to insist further upon it. John Stuart Mill,
who was certainly and perhaps more than anything a careful logician,
commences an exposition of the idealist thesis to which he was so
much attached, by carelessly saying: "It goes without saying that
objects are known to us through the intermediary of our senses.... The
senses are equivalent to our sensations;"[4] and on those propositions
he rears his whole system, "It goes without saying ..." is a trifle
thoughtless. I certainly think he was wrong in not testing more
carefully the solidity of his starting point.
In the first place, this limit set to our knowledge of the objects which
stimulate our sensations is only accepted without difficulty by
well-informed persons; it much astonishes the uninstructed when first
explained to them. And this astonishment, although it may seem so, is
not a point that can be neglected, for it proves that, in the first and
simple state of our knowledge, we believe we directly perceive objects
as they are. Now, if we, the cultured class, have, for the most part,[5]
abandoned this primitive belief, we have only done so on certain
implicit conditions, of which we must take cognisance. This is what I

shall now demonstrate as clearly as I can.
Take the case of an unlearned person. To prove to him that he knows
sensations alone and not the bodies which excite them, a very striking
argument may be employed which requires no subtle reasoning and
which appeals to his observation. This is to inform him, supposing he is
not aware of the fact, that, every time he has the perception of an
exterior object, there is something interposed between the object and
himself, and that that something is his nervous system.
If we were not acquainted with the existence of our nervous system, we
should unhesitatingly admit that our perception of objects consisted in
some sort of motion towards the places in which they were fixed. Now,
a number of experiments prove to us that objects are known to us as
excitants of our nervous system which only act on this system by
entering into communication, or coming into contact with, its terminal
extremities. They then produce, in the interior