Heterogony of ends
The "heterogony of ends" is a famous expression formulated in 1886 by German philosopher Wilhelm Wundt, to denote the phenomenon of how goal-directed activity often cause experiences that modify the original motivational pattern. 
This principle is exemplified in the emergence of new motives during the course of a chain of activities. For example, one may accept the invitation of a friend to attend an art show. Initially, the motive is simply the anticipation of a pleasant evening in good friendship, but in the course of the evening, one encounters a highly desirable work of art and wishes to purchase it. A whole new set of motives now enters the picture and now exist alongside and in addition to the original motive. The Heterogeny of Ends formulates that an ongoing behavioral sequence must often be understood in terms of ever-shifing patterns of primary and secondary goals. Another example would be how cat chasing a mouse may suddenly find it necessary to compete with a partner, overcome an unexpected barrier, or avoid a danger. Ends, goals, and purposes keep changing.
The original German expression was Heterogonie der Zwecke, variously translated in English as heterogony/heterogeneity/heterogenesis of ends/goals/purposes. It was first formulated by Wundt in 1886, in his book Ethics.
Notes and references
- Schneider, Louis (1986)Paradox and society: the work of Bernard Mandeville pp. 172–73
- Wundt (1886) Ethik. Eine Untersuchung der Thatsachen und Gesetze des sittlichen Lebens
- Wundt (1897) Ethics, an investigation of the facts and laws of the moral life translated from the second German edition (1892)
- txwes.edu Voluntarism, Structuralism, and Other Early Approaches to Psychology
- Cantfort History & Systems
- Nicola Abbagnano and Giovanni Fornero (2004) Diccionario de filosofía p. 542
- Max Harold Fisch Introduction to the English translation of The new science of Giambattista Vico, p.xxxii