Man is usually not content simply to register the observables that surround him; he needs to refer them as far as possible to the invariances of his environment.. The underlying causes of events, especially the motives of other persons, are the invariances of the environment that are relevant to him; they give meaning to what he experiences and it is these meanings that are recorded in his life space and are precipitated as the reality of the environment to which he then reacts.

p. 81 - The psychology of interpersonal relations, 1958