Abstract

In this paper the author analyzes the recent history of the concept of matter by examining two criteria, in-principle-observability and noncompositeness, for use of the term 'elementary particle'. Arguing that how these criteria are employed sheds light on a change in what matter means, the author draws three conclusions. Since the seventeenth century, in-principle-observability has undergone a progressive devaluation, if not abandonment, in favor of the criterion of theoretical simplicity. As a consequence, the concept of matter has undergone a "third phase" of dematerialization. Finally, the current concept of matter reveals a dilemma: if alleged elementary particles are verified through observation, they are composite and hence not elementary; if they are elementary, they are in-principle-unobservable