Cases, grammatical, 81. Causality, belief in a universal law of, 185 et seq. Cause, empirical origin of, 181; history of concept of, 180 et seq.; universalisation of the concept of, 185 et seq. Chaldæans, 173. Chance, idea of, 187 et seq. Charcot, 127. Chess-players, 40. Child, numeration in the, 35; general ideas of, 31 et seq.; time-sense of, 171. Chinese, 62, 69. Class, 211. Classification, biological, history of, 103 et seq., 204. Cognition, cardinal operations of, 1. Communication, 55 et seq. Compositors, 121. Concepts, 11, 92, 135; hierarchy of, 109, 213; relatively empty, 225; the inferior, 88; ultimate nature of, 113. Concrete type, 115. Condillac, 31, 77. Consciousness, the condition of any notion of time, 175 et seq. Convertibility, 192. Cope, 212. Copernicus, 197. Counting, 35, 99, 143. Cournot, 134, 146, 187, 188. Couturat, 144. Cross-breeding, 208. Cuvier, 107, 108. Czermak, 160. D’Alembert, 201. Damaras, 99. Darmesteter, 84. Darwin, 12, 18, 34, 63. Deaf-mutes, psychology of, 39; language of, 41; syntax of, 43; numeration in, 45; religious notions of, 46. Decimal system, 143. Declensions, 81. Delambre, 173. De Jussieu, 206. De Quincy, 150. Descartes, 197. Determinism, 188, 193. Dewey, 139. Dietze, 161. Differences, 90. Dissociation, 27. Dogs, intelligence of, 17, 20, 29. Dual, the, 77. Duck, 34. Dugas, 136. Duke of Argyle, 40. Duration, concrete, 159 et seq.; perception of, 161 et seq.; reproduction of, 162. Ebbels, 40. Economy of thought, 202. Effort, sense of, 182 et seq. Elephant, intelligence of, 15. Ellendorf, Dr., 13. Empirical laws, 198. Empiricists, 149. Energy, conservation of, 192. Esquimaux, 74. Euclidean geometry, 156 et seq. Evolution in our ideas, 195. Exchange, 110. Expectation, in reasoning, state of, 25. Extension, concrete, feeling of, 147 et seq.; characterised, 158. Extracts, 70. _Facultas signatrix_, 55. Family, 211. Ferrero, 220. First causes, 190. Fouillée, 177. Fox, ruses of, 18. Franklin, 55. Function, notion of mathematical, 190. Galileo, 190. Galton, 10, 40, 99. Gauss, 148, 156, 218, 220. Geese, time-sense of, 170. Geiger, 63. Genera, 210 et seq. General ideas, thinking by, 9; their grades distinguished, 101; likened to mental habits, 131, 225; meaning of, 135; observations on, 114 et seq. Generalisation, 9, 185. Generic image, 10, 87 et seq., 93, 169, 183, 196; an almost passive condensation of resemblances, 18; a spontaneous fusion of images, 22; comes half way between individual representation and abstraction properly so called, 23. Genii, 95. Geometry, born of practical needs, 148 et seq.; non-Euclidean, 156 et seq. Gérando, 40, 41, 51.