ABSTRACT
In the eighteenth century, Kant raised several objections against any form of psychology other than his own “transcendental” variety.5 He argued against the very possibility of both rational and empirical psychology, i.e., psychology based, respectively, on metaphysical rst principles or on introspective observation of subjective phenomena;6 the latter is especially germane here. Introspection, according to Kant, necessarily distorts, by participating in, the very phenomena it seeks to observe.7 Moreover, Kant held that psychology could never be a science inasmuch as the “exactness” of mathematics necessarily eluded it.8 What does this mean? A science is exact just when it can express its propositions mathematically. But for this to be possible, its objects must be capable of measurement; measurement in turn requires the xing of units. Physics can operate “exactly” because it possesses various exact units of measurement, such as joules or meters. But how could psychic phenomena (the “manifold of inner observation,” as Kant calls it)9 be measured? What unit of measurement could a psychologist employ in determining (mathematically) the ebb and ow of consciousness? These philosophical obstacles – introspection, exactness, psychic units, and psychic measurement – turn out, as we will see, to be evaded or ignored by the pioneers of experimental psychology: it does not begin as a self-conscious effort to reply to Kant. Rather, it is in the course of other scientic projects that problems of subjectivity ineluctably arise, e.g., in astronomy the discrepancy between observers’ reaction times in marking the movement of stars across a meridian, expressed in the so-called personal equation;10 and, more obviously, the phenomenology connected with the function of the nervous system. It was in fact a set of ingenious physiological experiments conducted by Weber that opened up the possibility, behind Kant’s back, as it were, of developing an experimental psychology; but it was only exploited in a philosophically, that is, psychologically self-conscious way by Fechner and his successors.11
