Language, differentiation of, [17];
origin of written, [18];
origin of verbal, [149];
origin of emotional, [220].
La Place's theory of planetary evolution, [263]-[265].
Laughter, common explanations of, [194];
movements in, [200];
groups of muscles successively affected in, [201];
caused by incongruities, [203];
facilitates digestion, [207].
Likeness and unlikeness, recognition of, the basis of classification, [147];
the basis of language, [149];
of reasoning, [150];
of art, [151];
leads to science, [152].
Manners, genesis of, [77];
decline of the influence of, [89];
conformity in manners leads to extravagance, [99];
conformity in, decreases social intercourse, [100];
defeats the true end of social life, [102], [107].
Muscular movements, cause of, [195];
arrested by feeling, [199];
in laughter purposeless, [201];
of animals when excited, [211];
variations of, produce changes of voice, [214].
Music, increasing heterogeneity of, [26];
relation of mental to muscular excitement, the source of, [214];
theory of, [221]-[224];
its history confirms the theory, [224]-[228];
negative proof of theory of, [228]-[231].
Nebula, are they parts of our siderial system? [243],
[249];
condensation of, [250];
motion in, [251];
significance of forms of, [254];
structure of spiral, [254].
Nebular hypothesis, [3], [34];
its high derivation, [239];
it explains cometary phenomena, [262].
Negative facts in geology, small value of, [362]-365.
Nervous system, effects of excitement in, [195];
directions of discharge of excitement in, [197];
course of discharge unguided by purpose, [201].
Previsions and ordinary knowledge, [117];
previsions known as science, [118];
common and scientific, [123];
when quantitative arose, [158];
increase in precision, [171].
Primary divisions of a germ and of a society, [404]-[407].
Progress, current meaning of, [1];
present inquiry concerning, [2];
law of progress exemplified in the genesis of solar system, [3];
in the phenomena of the earth's crust, [5];
in the advance of life in general, [7];
in the history of man, [10];
in the growth of civilization, [12];
in government, [13];
in language, [17];
in painting and sculpture, [20];
in poetry, music, and dancing, [24];
statement of the principle which determines progress of every kind, [32];
the principle of progress illustrated in geological phenomena, [35];
in chemical, [40];
in organic evolution, [42];
in social advancement, [50];
in use of locomotive engine, [54];
this principle does not explain things in themselves, [58];
progress of science, [141];
of astronomical discovery, [165], [171].
Progress of animals and societies in forming channels of communication, [416].
Psychology, relation of English thought to, [301];
classification in, for the present, must be provisional, [300], [301].