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7 Materialism: The Brain As Computer
objects have been taken away, leaving objects with no color, appearance, feel,
weight or any other discernible features. In fact, every feature which might
impact the senses—hence produce an impression of some kind—is absent
because in this hypothetical universe there is no life and there are no senses.
Everything material may be there, but not the senses. As Kant said about the
noumenal world (which is the same as the mind-independent world), nothing
can be said about its objects except that they exist.
In the absence of features of any kind, it is impossible to describe individual
objects and characterize them. What can be done instead is to compare things
with one another and define them in terms of each other. For example, a
straight line looks a certain way to the human eye—a way that makes us
recognize it as ‘straight’—and a heavy object makes itself known to our senses
by being hard to lift. But the ideal of objectivity requires that we reject these
interpretations of physical phenomena, because they rest on the idiosyncrasies
of sensory impressions.
Instead, we must treat the objects of study in a neutral fashion, based on
the way they relate to one another. For instance, we perceive a straight line as
the shape of a dangling plumb line. The path of an object in free fall is also
a straight line, and so is a taut string. In order to be “neutral”, you take the
notion of straight line to be an undefined concept, and record the fact that taut
strings, plumb lines and the paths of objects in free fall are straight lines. 8
If you aim for objectivity, you must then go one step further: When you
speak of a straight line in science, you must suppress the image of the taut
string in mind. You must force yourself to forgo any mental picture of what a
straight line looks like, and instead, think of it as nothing but an empty word.
When you use that word, you may hold the image of the taut string in mind,
but that’s for your own benefit: It may guide your intuition but should not
participate in your reasoning.
In order to carry out such a program, it is essential that the basic notions
(distance, mass, and so on) be treated as undefined concepts related to one
another by formal relations. Within the confines of scientific reasoning, these
entities must have no meaning. If you yield to the temptation to imagine them
in mind with a concrete meaning (for example, to imagine a line as the shape
of a taut string), you must be careful not to allow the meaning to slip into
your reasoning and play a role in your conclusions. For suppose you slip, and
continue to identify a straight line with a taut string. Suppose furthermore
that you make use of your mental image in scientific reasoning, so the validity
of your conclusion rests on the intuitive image.
If that were permitted, then the laws of science would depend on the meanings we attach to concepts—on the mental images we hold in mind. The laws
7 Materialism: The Brain As Computer
objects have been taken away, leaving objects with no color, appearance, feel,
weight or any other discernible features. In fact, every feature which might
impact the senses—hence produce an impression of some kind—is absent
because in this hypothetical universe there is no life and there are no senses.
Everything material may be there, but not the senses. As Kant said about the
noumenal world (which is the same as the mind-independent world), nothing
can be said about its objects except that they exist.
In the absence of features of any kind, it is impossible to describe individual
objects and characterize them. What can be done instead is to compare things
with one another and define them in terms of each other. For example, a
straight line looks a certain way to the human eye—a way that makes us
recognize it as ‘straight’—and a heavy object makes itself known to our senses
by being hard to lift. But the ideal of objectivity requires that we reject these
interpretations of physical phenomena, because they rest on the idiosyncrasies
of sensory impressions.
Instead, we must treat the objects of study in a neutral fashion, based on
the way they relate to one another. For instance, we perceive a straight line as
the shape of a dangling plumb line. The path of an object in free fall is also
a straight line, and so is a taut string. In order to be “neutral”, you take the
notion of straight line to be an undefined concept, and record the fact that taut
strings, plumb lines and the paths of objects in free fall are straight lines. 8
If you aim for objectivity, you must then go one step further: When you
speak of a straight line in science, you must suppress the image of the taut
string in mind. You must force yourself to forgo any mental picture of what a
straight line looks like, and instead, think of it as nothing but an empty word.
When you use that word, you may hold the image of the taut string in mind,
but that’s for your own benefit: It may guide your intuition but should not
participate in your reasoning.
In order to carry out such a program, it is essential that the basic notions
(distance, mass, and so on) be treated as undefined concepts related to one
another by formal relations. Within the confines of scientific reasoning, these
entities must have no meaning. If you yield to the temptation to imagine them
in mind with a concrete meaning (for example, to imagine a line as the shape
of a taut string), you must be careful not to allow the meaning to slip into
your reasoning and play a role in your conclusions. For suppose you slip, and
continue to identify a straight line with a taut string. Suppose furthermore
that you make use of your mental image in scientific reasoning, so the validity
of your conclusion rests on the intuitive image.
If that were permitted, then the laws of science would depend on the meanings we attach to concepts—on the mental images we hold in mind. The laws