c o N T E N T 5 Foreword by Arthur Danto ix xv Preface xix Introduction I Color Perception and Science The physical causes of color 1 The camera and the eye 7 Perceiving lightness and darkness 19 26 Chromatic vision Chromatic response 36 The structure of phenomenal hues 40 Object metamerism, adaptation, and contrast 45 Some mechanisms of chromatic perception 52 II The Ontology of Color Objectivism 59 Standard conditions 67 Normal observers 76 Constancy and crudity 82 Ch romatic democracy 91 Sense data as color bearers 96 Materialist reduction and the illusion of color 109 III Phenomenology and Physiology THE RELATlONS OF COLORS TO EACH OTHER 113 T he resemblances of colors 113 The incompatibilities of colors 121 Deeper problems 127 OTHER MINDS 134 Spectral inversions and asymmetries 134 vii CONTENTS I nternalism and externalism 142 Other colors, other minds 145 COLOR LANGUAGE 155 Foci 155 The evolution of color categories 165 Boundaries and indeterminacy 169 Establishing boundaries 182 Color Plates following page 88 Appendix: Land's Retinex Theory of Color Vision 187 Notes 195 Glossary of Technical Terms 209 Further Reading 216 Bibliography 217 Acknowledgments 234 Indexes 237 viii F o R E w o R D Very few today still believe that philosophy is a disease of language and that its deliverances, due to disturbances of the grammatical un­ conscious, are neither true nor false but nonsense. But the fact re­ mains that, very often, philosophical theory stands to positive knowledge roughly in the relationship in which hysteria is said to stand to anatomical truth. Freud said, famously, that hysteria appears to have no knowledge of physiology, for its paralyses and tics, its incapacities and pains, are located by the sufferer where there is no objective possibility of their occurring. Philosophers erase entities in defiance of common sense and postulate entities of which there is not the slightest possibility of scientific confirmation. Parsimonious with one hand and profligate with the other, philosophers behave not only as though they had no knowledge of scientific truth but as if philos­ ophy had its own authority, and not only did not need but could not use information from science. "Oh?" I have heard philosophers sneer when a bit of positive knowledge seemed to bear upon something they said or worried about, "I didn't think one had to know anything in order to do philosophy." My own etiology of this supercilious attitude takes us back to the Tractatus Logico-Philosophicus as its ultimate pathogen. On the one hand there is the celebrated dismissal of philosophical propositions as not really propositions at all, but symptoms of grammatical dis­ order. On the other hand there is the claim that "Philosophy is not one of the natural sciences," together with its parenthetical gloss that " The word 'philosophy' must mean something that stands above or below, but not beside the natural sciences." It must be such remarks as these that, encouraged the view that no natural science need be known by the philosopher in order to do philosophy. And this view remained when the other claims about philosophy-as-nonsense abated as the Verificationist Criterion of Meaningfulness itself slowly unraveled, leaving philosophers free to pursue their ontological ad­ ventures without regard to the cautions recommended by Verifica­ tionism, which is what Wittgenstein's bold diagnosis of philosophical language became in coarser minds than his. Free and independent of empirical constraints, philosophy began to establish a kingdom ix FOREWORD "above or below" the sciences and hence, with no real geographical relationship to the real world, which the natural sciences have it as their prerogative to represent and explain. In truth, I believe, the borders of philosophy remain vague and tentative, and more often than not philosophers believe themselves to be operating within their own domain when they have instead encroached upon the territories of positive knowledge and display analyses as their own which in fact collide with empirical truth. If philosophy indeed is autonomous to the point that it can be practiced in indifference to the actual world, then it plainly follows that if an analysis, presented as philosophical, in fact goes shipwreck against empirical truth, it was not philosophy to begin with. It was instead pre-emptive science hidden as such from its practitioners by a bad theory of philosophy and disguised as something higher or lower than natural science, when it was finally just bad science. The symptom­ atology of neurosis remains, even though all the warriors of thera­ peutic Positivism have died and their pennants lie trampled in the dust. The disease so much of philosophy consists of is the belief that it is philosophy when in fact it is something else. The topic of color provides a marvelous case study for the psy­ chotherapy of philosophy, for there is a rich-or at least copious­ literature devoted to it which has no value except as a symptom of something having gone wrong: its authors thought they were eluci­ dating conceptual structures-lithe logic of our language" -when their problems had to do not with concepts or logic or language, but with the way the world is given to us. That something could not be at once all-over red and all-over green was widely accepted by phi­ losophers as true, but they saw it as their task to analyze the 11 could not" in the claim and hence the status of the proposition with which it was expressed. Was it analytic and hence a matter of meaning? Or synthetic but necessary and hence a matter of something far less well understood? It certainly did not appear to be the sort of logical in­ compatibility involved in 1150mething could not at once be all-over red and not all-over red." For that would suggest that something could not at once be all-over blue and all-over red, when in fact there are reddish blues and bluish reds. But there are not-and it seemed could not be-reddish greens and greenish reds. David Pears wrote an article deemed sufficiently important to pub­ lish in an anthology, Logic and Language (both volumes of which were canonical reading in the 1950s), on the topic of color incompatibilities. According to Pears, the puzzling sentence seemed both a priori and true. 50 it was dismissed a priori, we might say, as a posteriori. If it x FOREWORD were a posteriori and contingent, one could look for exceptions. But­ and the riposte typifies the official philosophical attitude of the era­ " Anyone who began to look for exceptions would betray that he did not really understand the sentence." Since Pears saw no way in which there could coherently be exceptions, and no way either in which it could rest on a matter of meaning or of logic, he found the "could not" baffling and almost incomprehensible. Pears might have found some help had he considered some further color relationships in his discussion. It would be curious, for exam­ ple, that 'red' and ' green' should be incompatible as terms when 'red' was not incompatible with 'yellow.' Or that red and green could not co-occupy the same area when red and yellow were as chummy as coffee and cream. Convinced as he was that the problem was essen­ tially philosophical and that philosophy analyzes language, he turned at right angles from where the truth was to be found, and addressed himself, with characteristic-if, in this instance misdirected-inge­ nuity, to rules of designation: semantical epicycles, as it were, in­ serted to preserve the autonomy of philosophy. Of course the information he needed, to turn aside from the prob­ lem as not philosophical at all, was not widely available at the time. Logic and Language: Series II was published in 1953. The crucial paper of Hurvich and Jameson, "An Opponent-process Theory of Color Vi­ sion" came out in the Psychological Review in 1957, though preliminary studies appeared as early as 1955. The red-green incompatibility had to do neither with language nor with colors, considered in abstraction from optical physiology. It had to do rather with how we are made, with how color is processed behind the retina, and with this discov­ ery an entire philosophical literature shivered into disuetude. The problem never had been philosophical. The philosophers who dealt with it were doing anticipatory science badly. Their thought was as obsolete as astrology. 'II am not the outcome or meeting point of nu­ merous causal agencies which determine my bodily or psychological make-up," Merleau-Ponty wrote, wrongly, rejecting as not to the point for self-understanding exactly what was to the point. How we see is what we are. In the September 9, 1983, issue of Science, I read a paper with a title that ought to have been evidence that its authors did not un­ derstand their language, had Pears been right: 'IOn Seeing Reddish Green and Yellowish Blue." From the perspective of conceptual anal­ YSIS, th1s would have been like coming across an article called liOn Squaring the Circle and Duplicating the Cube." One ought to have known, a priori, that the paper, if not merely jocular or arch, must be xi FOREWORD incoherent or false. Instead, the article in Science was informative and true, its title descriptively accurate, and it reported certain exceptions to the misclassified statement regarding red-green incompatibility, now seen to be a posteriori and admitting of exceptions. Its II Abstract" read as follows: Some dyadic color names (such as reddish green and bluish yellow) de­ scribe colors that are not normally realizable. By stabilizing the retinal im­ age of the boundary between a pair of red and green stripes (or a pair of yellow and blue stripes), but not their outer edges, however, the entire region can be perceived simultaneously as both red and green (or blue and yellow).