Abstract.—Allport objects to operational definitions of personality because, by equating personality with observable phenomena, they reduce personality to something subjective. His view on the reality of phenomena is, however, but one of several possible. The plea for an operational definition of personality may equally well be based on the phenomenological assumption that to exist means, for man, to appear in the world for someone, and what appears for someone does not have to be thought of as existing in that someone's mind. To be studied empirically, personality must be knowable, and it must be defined in terms of how it is known. Postulating an internal structure behind or within the phenomena known as personality, adds no meaning to the concep