Page:Philosophical Review Volume 3.djvu/241



PSYCHOLOGICAL.

The author's conclusions may be summarized as follows: (1) No one has ever seen light of one wave-length. (2) No conclusion may be drawn from the mixture of the colors of a dispersion- spectrum as regards an exceptional position of certain wave- lengths. (3) Purple is a component of white light, on the same level as any other color-quality. (4) Not only are spectral colors not perfectly pure: they are not equally pure in the same spectrum. [Criticism of the color-triangle construction.] (5) Definition of normal and color-blind vision. (6) Vision is achromatic, dichro matic, or polychromatic. [Criticism of Helmholtz.] (7) For poly chromates no universally valid distinction of ground-sensations or primary valences can be made. (8) Not all polychromates are normal. (9) There are various modes of transition from normal polychromatism to pure dichromatism: not every case of anomalous polychromatism presents such a transition-mode. (10) Dichroma tism does not display any constant preference in the matter of its two ground-colors. (11) There may be wanting the sensibility to any particular spectral quality, in dichromatism and polychromatism: there may be a transference of complementarism. (12) The 'neutral line' of color-blindness does not always by any means lie where it should, according to the ground-color theories. [Illustrations from ten cases.]