1. First published in Perception and Personal Identity, Norman S. Care and Robert H. Grimm (eds.), The Press of Case Western Reserve University, Cleveland, 1969, pp. 140–173
2. In Logic and Ontology (Studies in Contemporary Philosophy), Milton K. Munitz (ed.), New York University Press, New York, 1973.
3. David Katz, The World of Color, Kegan Paul, London 1935. Cf. also Jacob Beck, Surface Color Perception, Cornell University Press, Ithaca, N.Y., 1972, Ch. 2.
4. Cf. my paper, ‘The Semantics of Modal Notions and the Indeterminacy of Ontology’, in Semantics of Natural Language, D. Davidson and G. Harman (eds.), D. Reidel Publishing Company, Dordrecht, 1972, pp. 348–414, reprinted as Chapter 2 of the present volume.
5. This spurious problem is discussed at length e. g. in G. J. Warnock, ‘Seeing’, Proceedings of the Aristotelian Society
55 (1954–55).