ed degree, of
course, animals have vocal and gesture habits; specific cries of
hunger, of sex desire, or distress. But they cannot, with their
limited number of vocal mechanisms, possibly develop language
habits, develop a system of sounds associated with definite
actions and capable of controlling actions. Only human
beings can produce even the simplest system of written symbols,
by which visual stimuli become symbols of actions, objects,
emotions, or ideas. Biologists--in particular the experimentalist,
Watson--find, in the capacity for language,
man's most important distinction from the brute.

Language may be said, in fact, to be the most indispensable
instrument of civilization. It is the means whereby the whole
life of the past has been handed to us in the present. It is the
means whereby we in turn record, preserve, and transmit our
science, our industrial methods, our laws, our customs. If
human relations were possible at all without a language, they
would have to begin anew, without any cultural inheritance,
in each generation. Education, the transmitter of the
achievements of the mature generation to the one maturing,
is dependent on this unique human capacity to make seen
marks and heard sounds stand for other things. The extent
to which civilization may advance is contingent upon the
development of adequate language habits. And human beings
have perfected a language sufficiently complicated to
communicate in precise and permanent form their discoveries of
the complex relations between things and between men.

MAN THE ONLY MAKER AND USER OF TOOLS. One of the most
important ways in which man is distinguished from the lower
animals is in his manufacture and use of tools. So far as we
know the ability to manufacture and understand the use of
tools is possessed by man alone. "Monkeys may be taught a
few simple operations with tools, such as cracking nuts with
a stone, but usually they merely mimic a man."[1] Man's
uniqueness as the exclusive maker and user of tools is made
possible by two things. The first is his hand, which with its
four fingers and a thumb, as contrasted with the monkey's
five fingers, enables him to pick up objects. The second is his
capacity for reflection, presently to be discussed, which
enables him to foresee the consequences of the things he does.

[Footnote 1: Mills: _The Realities of Modern Science_, p. 1.]

The use of tools of increasing refinement and complexity is
the chief