There can be no doubt that an important movement in psychology has
arisen in recent times through the effort to approach the phenomena of
mind from the experimental and physiological point of view. Different
students of psychological science will estimate differently both the net
result already reached by this effort and the promise of further
additions to the sum of our knowledge from continued investigation of
the same kind. Some writers have certainly indulged in extravagant
claims as to the past triumphs of so called Physiological Psychology,
and in equally extravagant expectations as to its future discoveries. On
the other hand, a larger number, perhaps, have been inclined either to
fear or to depreciate every attempt to mingle the methods, laws, and
speculations of the physical sciences with the study of the human soul.
These latter apparently anticipate that some discovery in the
localization of cerebral function, or in psychometry, may jeopard the
birthright of man as a spiritual and rational being. Or possibly they
wish to regard the soul as separated, by nature and with respect to its
modes of action, from the material body in such a way as to render it
impossible to understand more of the one by learning more about the
other. As a result of some years of study of the general subject, I
express with considerable confidence the opinion that there is no ground
for extravagant claims or expectations, and still less ground for any
fear of consequences. In all cases of new and somewhat rankly growing
scientific enterprises, it is much the better way to waive the
discussion of actual or possible achievements, as well as of welcomed or
dreaded revelations of new truth, and proceed at once to the business on
hand. It is proposed in this book to follow this better way. It will be
the task of the book itself to set forth the assured or alleged results
of Physiological Psychology and this will be done at every step with
such degree of assurance as belongs to the evidence hitherto attainable
upon the particular subject discussed With declamation, either in attack
or defence of the old psychology of the introspective method, etc., one
may dispense without serious loss. The study of the phenomena of
consciousness by tho method here proposed necessarily requires some
acquaintance with a consider able circuit of sciences which are not
usually all alike closely allied. The number of scholars who can form
opinions with equal freedom and confidence in all of these sciences is
very small. Moreover, since all psycho-physical laws are supposed as the
very term indicates to govern the correlations of phenomena with
phenomena of the nervous system, a peculiar mystery belong to much of
the domain withiri which psycho-physical science i compelled to move.
These facts may fitly, on tho one hand, excite caution in the writer
and, on the other hand, exciiso him for many inevitable failures to set
forth with perfect definition and confidence the conclusions he has to
propose. Much will bo said thai must be accepted as provisional, as only
probably true. Much room must also be made for conjecture and
speculation. What IB most important, however, is that conjecture should
not boptit forth as ascertained fact, or speculation as unquestioned
law. It would have been a great assistance to mo if I had had more
predecessors in the path which I am to take. But with tho exception of
Wundts masterly work Grundzttye der phyxiohxjiwhtn Psychologies second
edition in 1880, no ouo book han attempted to cover, even in a summary
way, the entire ground...
