Though the subject of this work, "nominalism and contemporary nom inalism," is philosophical, it cannot be fully treated without relating it to data gathered from a great variety of domains, such as biology and more especially ethology, psychology, linguistics and neurobiology. The source of inspiration has been an academic work I wrote in order to obtain a postdoctoral degree, which is called in Belgium an "Aggregaat voor het Hoger Onderwijs" comparable to a "Habilitation" in Germany. I want to thank the National Fund of Scientific Research, which accorded me several grants and thereby...