Farradane's categories of relations (Fig. 1) are viewed as percepts rather than concepts. It is argued that Farradane's original use of language supports this view. A comparison of Farradane's categories with perceptual discriminations in humans is attempted. The conclusion seems to support claims made for relational operators, whether those of Farradane or similar relational indexing devices as in PRECIS, to have the potential to act as metalanguages.