The painter who works on his public’s emotions with an end in view is a propagandist with the outlook of the poster artist. He does not intend his public to be free in its choice of the use to which it puts the communication he makes. Verbal expression must be limited so that it expresses truth without any implication other than the implication that it is true in the analyst’s opinion. By considering psycho-analytic experience in the light of a theory of transformations it is possible to see the problems of thinking afresh. Freud associated thinking with the dominance of the reality principle and showed that it interposed a stage between awareness of an impulse and the action necessary for its fulfillment; he drew attention to its ameliorating effect on frustration. A mathematical illustration is afforded by the use of numbers for enumeration and record.