This paper discusses the notion of categorial difference as delineated by Ryle in his two famous essays Categories (1938) and Philosophical Arguments (1945), where it appeared strictly linked to that of categorial mistake. Actually, neither of these concepts is properly defined by Ryle, who rather exemplifies them informally and intuitively, and offers some criteria for their correct individuation and treatment. ‘Logical form’ and ‘logical power’ are the two cardinal notions of the Rylean analysis, and of his attempt to characterize categorial confusion in terms of logical absurdity or nonsense. In showing the critical aspects of such an attempt, Strawson, in turn, proceeded to a global reformulation of the question and concept of categorial difference; nevertheless, also his theory is criticized as inadequate by J. Dancy in a recent (2014) miscellaneous volume on Ryle edited by D. Dolby. In another essay of this volume, Ryle’s and Strawson’s models are examined by H. J. Glock on the background of Quine’s Attack on the ‘analytic/synthetic’ distinction, and of more recent views on semantic nonsense and meaning compositionality.

Keywords: Absurdity; Category; Category Mistake; Logical Form; Meaning; Nonsense; Quine; Ryle; Strawson.