Abstract
This article deals with the categorisation of things contained in the treatise On The Riverbed (De alveo) by Bartolus de Saxoferrato, a representative of the mediaeval Italian school of legal commentators. With the intention of showing what constitutes the essential form of things, with which their existence is linked, he divides them into several categories, namely material and immaterial (corporales and incorporales), natural and artificial (naturales and artificiales), endowed with spirit and not endowed with spirit (animatae a inanimatae).
For things endowed with spirit he further istinguishes whether it is living, perceptive or rational (anima sensitiva, vegetativa, intellectiva). Only humans possess a rational spirit.
Bartolus bases his division on the categories of Roman law but connects it with the thoughts of his time, influenced by scholasticism, and so some of the ategories used cannot be found in legal sources, but for example in the Summa Theologica.