  Thomas of Erfurt belonged to an interesting though somewhat obscure group of late thirteenth- and early fourteenth-century philosophers known as the speculative grammarians or Modistae.  The term ‘speculative grammarian’ is ambiguous because it is also used by historians of medieval philosophy to refer to twelfth-century Parisian grammar masters such as William of Conches, Peter Helias, and Ralph of Beauvais, who systematically revised the ancient grammars of Donatus and Priscian — textbooks used to teach Latin to schoolboys  — to produce a universal  semantics.[7]  The two groups are related, as it turns out, since these latter-day grammarians adopted many of the theories as well as the universalizing tendencies of their twelfth-century predecessors.  Foremost among them was the theory of the modi significandi, or modes of signifying. The term ‘Modistae’ or ‘Modist’ properly refers to the later group.