[98] The most interesting discussion of these topics I know is that of Friedrich Paulsen, in his _Introduction to Philosophy_ (translated by Professor Frank Thilly). [99] _Cf._ Perry, R. B., "The Hiddenness of the Mind," _Jour. of Phil., Psy., and Sci. Meth._, Jan. 21, 1909; "The Mind Within and the Mind Without," _Ibid._, April 1, 1909; "The Mind's Familiarity with Itself," _Ibid._, March 4, 1909. Urban, W. M., _Valuation_, p. 243. [100] Davenport, _op. cit._, p. 331. CHAPTER IX THE SOCIOLOGICAL PRESUPPOSITIONS Conceptions of the social unity fall, in the main, into three classes: the mechanical, the biological, and the psychological. Each of these conceptions recognizes, of course, that the individual has a mind, but the first thinks of that mind as so shut in that the only connections between men must be of an external sort; the second sees modes of collective action _analogous_ to the modes of individual action, and reaches the conception of a social mind by analogy; while the third treats the social mind as an empirical fact, the phenomena of which can be studied as concrete things in detail. And there are gradations here, and combinations. The following extract, freely translated and substantially abridged, is taken from chapter I of DeGreef's _Introduction a la Sociologie_:-- It is in vain that Spencer protests against the accusation that he has assimilated the laws of biology with those of sociology. The confusion is everywhere complete. He has not indicated a single law, nor a single phenomenon, which has not its correspondent, if not its equivalent, in the antecedent sciences. Draper, in his _History of the Intellectual Development of Europe_, adopts precisely the doctrine that the laws of biology apply equally to sociology. Man is the archetype of society. Nations pass through their periods of infancy, adolescence, maturity, age, death. This sort of thing makes sociology wholly unnecessary. The attempt of Stanley Jevons to explain economic crises by sun-spots, so far from being an effort of genius, is simply a _jeu d'esprit_. It is simply a recognition of the common fact that climate is one of the factors that influence man in society. According to Hesiod, physical forces first engender each other, then in turn the gods and man. Since then, social science has in turn been founded on the laws of astronomy, chemistry and biology. To-day it is the last, vitiated, further, by false psychological notions about the power and unlimited liberty of the reason, and the consciousness of human individuals, and applied by analogy to the collective reason.