On the Use of the Psi Hypothesis in Psycho-Analysis1

A new concept usually has trouble making its way into the marrow of an empirical science. It cannot be appreciated all at once as an abstract principle applicable to a general class of data but has to be 'worked through' in a thousand concrete instances before it begins to take hold as part of the ego so to speak, of the science.

Emotional resistances are always to some degree responsible for the difficulties encountered by an unfamiliar concept. In the case of what has come to be called the psi hypothesis this is particularly evident, and there are indeed good grounds for it. But such resistances obviously cannot be handled while confusion and obscurity still prevail on the logical side of the picture; and this, unfortunately, is still true of the psi hypothesis the minute it is taken out of the laboratory, where pretty demonstrations can be arranged under conditions of experimental isolation and control, and left to fend for itself in the rough and tumble of life in the raw. Here a major difficulty arises when people demand that 'psi', which must necessarily now travel under the incognito and in the crude garments of the itinerant postulate, still reveal itself with its clear and unsmudged laboratory visage before they will open their doors to it. But this is no more possible in the case of psi than in the case of any construct which leads the double life of demonstrable 'fact' in the laboratory and hypothesis looking for work on the outside. Unfortunately, moreover, psi is in the class of construct-facts (along with 'the unconscious' and 'evolution') that are burdened with the peculiarity of having nothing about them which sets geiger counters clicking or causes litmus paper to change colour; it is recognizable only by the fact of the work it can do when given a trial.

In the following account of certain events the psi hypothesis will be given a modest job to do. Whether it acquits itself as well as or better than other hypotheses which also can be brought i