ain a single thought process, for
such process always involves the participation of many functions whose
separate roles are impossible to distinguish accurately. Instead of
measuring the intensity of various mental states (psycho-physics), it is
more enlightening to measure their combined effect on adaptation. Using
a biological comparison, Binet says the old "faculties" correspond to
the separate tissues of an animal or plant, while his own "scheme of
thought" corresponds to the functioning organ itself. For Binet,
psychology is the science of behavior.

BINET'S CONCEPTION OF GENERAL INTELLIGENCE. In devising tests of
intelligence it is, of course, necessary to be guided by some
assumption, or assumptions, regarding the nature of intelligence. To
adopt any other course is to depend for success upon happy chance.

However, it is impossible to arrive at a final definition of
intelligence on the basis of _a-priori_ considerations alone. To demand,
as critics of the Binet method have sometimes done, that one who would
measure intelligence should first present a complete definition of it,
is quite unreasonable. As Stern points out, electrical currents were
measured long before their nature was well understood. Similar
illustrations could be drawn from the processes involved in chemistry
physiology, and other sciences. In the case of intelligence it may be
truthfully said that no adequate definition can possibly be framed which
is not based primarily on the symptoms empirically brought to light by
the test method. The best that can be done in advance of such data is to
make tentative assumptions as to the probable nature of intelligence,
and then to subject these assumptions to tests which will show their
correctness or incorrectness. New hypotheses can then be framed for
further trial, and thus gradually we shall be led to a conception of
intelligence which will be meaningful and in harmony with all the
ascertainable facts.

Such was the method of Binet. Only those unacquainted with Binet's
more than fifteen years of labor preceding the publication of his
intelligence scale would think of accusing him of making no effort to
analyze the mental processes which his tests bring into play. It is true
that many of Binet's earlier assumptions proved untenable, and in this
event he was always ready, with exceptional candor and intellectual
plasticity, to acknowledge his error and to plan a new line of attack.

Binet's conceptio