294 The American Naturalist. [March, 
must remember that psychophysics is itself in the experimental stage, 
and, until methods of experiment in these new fields have been devised 
and perfected, we cannot expect definite results. 
There has recently been developed, also within the limits of psy- 
chology proper, another discipline known as physiological psychology. 
It endeavors to determine the physiological conditions of consciousness, 
and, more particularly, the relation of the different qualities of con- 
sciousness to the several cortical areas. Much light has been thrown 
upon these problems, and, as one chief result, it is possible to introduce 
into introspection a precision before unknown. The English associa- 
tionists have taught us, for example, on the basis of purely introspec- 
tive evidence, that our ideas of physical things are complexes, contain- 
ing visual, auditory, tactual and other elements—-that what we call 
“ knowledge” is a mass of dim, subconscious associations. Researches 
into the physiology of the brain have shown that color, sound and mo- 
tion certainly, and probably touch, are related to different cortical 
areas—that lesions of portions of the cortex will destroy knowledge 
without impairing sensation. This at once supports the conclusions 
of introspection and enables us to form more accurate conceptions of the 
complex processes involved. 
In England, the home par excellence of introspective psychology, 
Mr. Francis Galton, in his epoch-making book, “ Inquiries into Human 
Faculty,” has called attention to the mental idiosyncrasies of individ- 
uals. More recent workers in the same line have shown conclusively 
that introspection cannot give results that will be, in all cases, true. It 
is impossible to overestimate the importance of this discovery, and 
there is nothing more surprising than that a fact at once so important 
and so easily ascertained, should have escaped notice for more than two 
thousand years. Since the early days of Greek philosophy, for exam- 
ple, the Nominalists and the Conceptualists have waged unending war- 
fare; the Conceptualists maintain that the name of a class awakens an 
idea or mental state that is not representative of any member of that 
class; the Nominalists, on the contrary, hold that the class name either 
awakens a concrete image of a particular member of the class, or else 
it awakens no mental state whatever—it is a mere flatus vocis. And 
now we know that both are right. Each was describing what intro- 
spection revealed to him, and abusing his fellow-student for doing like- 
wise. 
Mr. Galton’s discovery of the idiosyncrasies of the individual has 
not only showed the limitations within which alone introspection can 
be used, but has served to call attention to other forms of comparative 
