The dissertation examines the categorial system proposed by Whitehead in his “Process and Reality” (1929). This system is analysed and discussed by means of comparisons with other categorial systems (those of Aristotle, Kant, Alexander). The analysis shows the singularity of Whitehead’s position, and, by analysing the way in which Whitehead makes use of his categorial system in “Process and Reality”, suggestion is made that the roots of