The evolution of grammatical categories is usually shown as a diagram, where the number of parts of speech gradually increases. This paper intends to put some of these given facts into question, and show that the history of particles goes even beyond Plato.

Particles were an object of study not only for ancient philosophers and grammarians but also for the rhetoricians and for the philologists of Alexandria. Each if these branches of inquiry added some new feature to the notion of the category particle. Traces of those ancient studies are still visible in our present grammars.

Among the subclasses of particles there has always been one, which is especially mysterious: in Greek these words were called 'parapleromatikoi', in Latin they appeared as 'completivae' or 'expletivae', and presently elements of the same kind are called 'pragmatic particles' or 'discourse particles', in German Abtönungspartikeln or Modalpartikeln.

A typical feature of these elements is that in many languages they have a homonymous form conveying other functions. The function and meaning of a particle can only be specified in the context of its appearance. This can be seen as a fundamental difference between the cluster of declinable and indeclinable words, between the referential and non-referential words.

In this paper, rhetoric, Alexandrian linguistics and Stoic language philosophy are dealt with as the origins of the representation of the particles. Subsequently, I will follow up their description in early vernacular grammars and briefly touch the particles in grammars of the 17th and 18th century. I also intend to show, which questions about particles have been discussed repeatedly. All this will be compared with our present view of the particles.