The term „productive“ is also apt to be confused with „active,“ and „productiveness“ with „activity.“ While the two terms can be synonymous (for instance, in Aristotle’s concept of activity), activity in modern usage frequently indicates the very opposite of productiveness. Activity is usually defined as behavior which brings about a change in an existing situation by an expenditure of energy. In contrast, a person is described as passive if he is unable to change or overtly influence an existing situation and is influenced or moved by forces outside himself. This current concept of activity takes into account only the actual expenditure of energy and the change brought about by it. It does not distinguish between the underlying psychic conditions governing the activities. ― (1947a: Man for Himself. An Inquiry into the Psychology of Ethics, New York (Rinehart and Co.) 1947, p. 85.)

Activity in the modern sense refers only to behavior, not to the person behind the behavior. It makes no difference whether people are active because they are driven by external force, like a slave, or by internal compulsion, like a person driven by anxiety. (…)The modern sense of activity makes no distinction between activity and mere busyness. ― (1976a: To Have Or to Be?, New York (Harper and Row) 1976, p. 90.)