So far we have been speaking repeatedly of an "external
world" and a world of perceptions formed in our brain, the latter of which is the one
we see. However since we can never actually reach the "external world", how can
we be sure that such a world really exists?
Actually we cannot. Since each object is only a collection of
perceptions and those perceptions exist only in the mind, it is more accurate to say that
the only world that really exists is the world of perceptions. The only world we know of
is the world that exists in our mind: the one that is designed, recorded, and made vivid
there; the one, in short, that is created within our mind. This is the only world we can
be sure of.
We can never prove that the perceptions we observe in our brain have
material correlates. Those perceptions may well be coming from an "artificial"
It is possible to observe this. False stimulations can produce in our
brain an entirely imaginary "material world". For example, let us think of a
very developed recording instrument where all kinds of electrical signals can be recorded.
First, let us transmit all the data related to a setting (including body image) to this
instrument by transforming them into electrical signals. Second, let us imagine that you
can have your brain survive apart from your body. Lastly, let us connect the recording
instrument to the brain with electrodes that will function as nerves and send the
pre-recorded data to the brain. In this state, you will feel yourself as if you are living
in this artificially created setting. For instance, you can easily believe that you are
driving fast on a highway. It never becomes possible to understand that you consist of
nothing but your brain. This is because what is needed to form a world within your brain
is not the existence of a real world but rather the availability of stimulations. It is
perfectly possible that these stimulations could be coming from an artificial source, such
as a recorder.
In that connection, distinguished science philosopher Bertrand Russell
As to the sense of touch when we press the table with our fingers, that
is an electric disturbance on the electrons and protons of our fingertips, produced,
according to modern physics, by the proximity of the electrons and protons in the table.
If the same disturbance in our finger-tips arose in any other way, we should have the
sensations, in spite of there being no table.(148)
It is indeed very easy for us to be deceived into deeming perceptions
without any material correlates as real. This is exactly what happens when we dream.
Stimulations coming from an object are converted into electrical signals and cause
an effect in the brain. When we "see", we in fact view the effects of these
electrical signals in our mind.