The Union of the Psychical and the Physical in the
Organism. -- We shall now examine some of the evidence con-
firmatory of our assertion in the last chapter, that conscious
processes and physiological processes are intimately connected
in the organism. We shall in this way discover some of the
reasons why it is desirable for us at the outset of our study
of mental life to learn something about the nervous system,
to which subject we shall then devote the remaining portion
of the chapter.

Evidence from Familiar Facts. -- Common observation
informs us of at least two fundamental types of fact con-
cerning these mind-body relations. We know in this manner
(1) that our consciousness or knowledge of the world about
us depends primarily upon the use of our senses. A person
born blind and deaf has neither visual nor auditory sensa-
tions or ideas, and never can have, so long as he remains desti-
tute of eyes and ears. By means of the other senses he may
be taught much about colours and sounds, as Helen Keller
has been, who lost her sight, and hearing in infancy; but he
never can have the experience which you or I have, when we
see a colour or hear a sound, or when we permit a melody
"to run through our heads," as we say, or when we call into
our minds the appearance of a friend's face. Indeed, if a
child becomes blind before he is five years old he commonly
loses all his visual ideas and memories just as completely as
though he had been born blind. There is every reason to
believe that if we were deprived of all our senses from birth,

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