LECTURE  II

§ I. Analysis of Mental Processes. § II. Idea and Sensation.
§ III. Intensity and Quality of Sensation. § IV. Measure¬
ment OF THE Intensity of Sensation.

§ I

So soon as ever the dawn of knowledge had broken upon
us through the portals of the senses, we began to compare
objects, to reflect upon them. Tlje first work of thought was to
set things in their places, to transform the chaos of sense-
impressions into an intelligible cosmos. But after everything
else has been arranged, there still remains something which has
as yet no place,—ourselves : our feeling, willing, and thinking ;
so that the question arises : how can our own mental life be
made the subject of investigation like the objects of this external
world of things about us ? And yet—can such a question be
asked .' Is it not really self-contradictory ? It is as though we
required that the tone should hear itself, or the ray of light be
sensed by itself

It is, indeed, true that here, as we enter upon the study of
psychology, a peculiar difficulty presents ^itself If we try to
observe our mental activities, the observer and the observed
object are one and the same. But the most important condition
of a trustworthy observation is always thought to consist in the
mutual independence of object and observer. Nevertheless, we
should be overhasty if we disputed the possibility of psy¬
chological observation in general because of this unavoidable
limitation of the science. Only so much is true : that the
peculiarities of the object, in this case as in others, imply special
conditions of its observation. These can be stated in two rules.
First: so long as we confine ourselves to introspection, without
calling in any assistance from outside, mental processes may not
be observed directly while they are taking place.     We must