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are rare, the proof that two events occurring in the same brain are spatially and temporally related — these are principles which permit of the investigation of causal connections in the psychic sphere. Such a knowledge of causal connections requires for its proof or for its refutation an understanding of the probability- factors involved. Bleuler here desires only to draw attention to the importance of an understanding of psychological probability. As an example of an investigation of the kind required, he takes Freud's analysis of the 'aliquis' case. Here he finds that: (1) the forgetting of so ordinary and so colourless a word is — by itself — an extremely rare occurrence, (2) the splitting up of the forgotten word into a and liquis has again — in itself — an extremely low probability (perhaps 1 in 100,000), (3) of the succeeding ten asso- ciations nine have a distinct relationship to the 'period complex', (4) in addition to this we have to take into consideration the general fact of the repression of unpleasant complexes. Thus the evidence in favour of the proposed interpretation of the case is very strong; the probability-factors support the existence of the supposed causal connection.
D. FUNDAMENTAL PRINCIPLES OF MENTAL PROCESS INFLUENCE OF AFFECTIVE TONE
According to Fedem (4), who follows a step further Freud's line of thought upon this subject, both the unconscious and con- sciousness work according to the pleasure-' pain' principle, while consciousness works also to some extent according to the reality- principle, which latter signifies a freeing of thought from' the in- fluence of affect. The reality-principle is intimately connected with the idea of time, and it produces associations in terms of caus- ality rather than in terms of affect. The inhibition of the pleasure- 'pain' principle is carried out by 'conscience' in the ' ethical stage ', working through the agency of fear. The ability to endure 'pain' is a necessary condition which has to be fulfilled before the real- ity-principle can become effective.
The principle of adaptation to reality as one of the fundamen- tal principles of thought is mentioned by various authors (Freud, Bleuler, Schilder). According to Pikler, however (24, 25), adapt- ation constitutes the one fundamental characteristic of all cognitive
