In the psychological fields most fundamental to the whole behavior of living things the transition seems inevitable to a Galileian view of dynamics, … - Kurt Zadek Lewin

One can ask two different kinds of questions with regard to the topics of study in psychology as well as in other sciences. One can ask for the phenomenal characteristics of psychological units or events, for example, how many kinds of feelings can be qualitatively differentiated from one another or which characteristics describe an experience of a voluntary act. Aside from this are the questions asking for the why, for the cause and the effect, for the conditional-genetic interrelations. For example, one can ask: Under which conditions has been a decision made and which are the specific psychological effects which follow this decision? The depiction of phenomenal characteristics is usually characterized as “description”, the depiction of causal relationships as “explanation.”

A successful individual typically sets his next goal somewhat but not too much above his last achievement. In this way he steadily raises his level of aspiration... The unsuccessful individual on the other hand, tends to show one of two reactions: he sets his goal very low, frequently below his past achievement... or he sets his goals far above his abilities.

For Aristotelian physics the membership of an object in a given class was of critical importance, because for Aristotle the class defined the essence or essential nature of the object, and thus determined its behavior in both positive and negative respects.