Dreams

530 Medical psychology differs from all other scientific disciplines in that it has to deal with the most complex problems without being able to rely on tested rules of procedure, on a series of verifiable experiments and logically explicable facts. On the contrary, it is confronted with a mass of shifting irrational happenings, for the psyche is perhaps the most baffling and unapproachable phenomenon with which the scientific mind has ever had to deal. Although we must assume that all psychic phenomena are somehow, in the broadest sense, causally dependent, it is advisable to remember at this point that causality is in the last analysis no more than a statistical truth. Therefore we should perhaps do well in certain cases to make allowance for absolute irrationality even if, on heuristic grounds, we approach each particular case by inquiring into its causality. Even then, it is advisable to bear in mind at least one of the classical distinctions, namely that between causa efficiens and causa finalis. In psychological matters, the question “Why does it happen?” is not necessarily more productive of results than the other question “To what purpose does it happen?”

531 Among the many puzzles of medical psychology there is one

^l [First published as “Vom Wesen der Traume,” Ciba-Zeitschrift (Basel), IX : 99 (July, 1945). Revised and expanded in Vber psychische Energetik und das Wesen der Traume (Psychologische Abhandlungen, II; Zurich, 1948).—EDITORS.]

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