LOGIC He has a high self-respect and places great value upon social distinction He laments the great part that rowdyism and unrefined good-fellowship play in the dealings of American politicians with their constituency He holds that monetary considerations should usually be the decisive ones in questions of public policy He respects the principle of individualism and of laissez-faire as the greatest agency of civilisation These views, among others, I know to be the obtrusive marks of a ‘mugwump’ Now, suppose I casually meet a man in a railway train and falling into conversation find that he holds opinions of this sort; I am naturally led to suppose that he is ‘mugwump’ That is hypothetic inference That is to say, a number of readily verifiable a marks of a mugwump being selected, I find this man has these, and infer that he has all the other characters that go to make a thinker of that stripe (EWP 210) This homespun example illustrates the three stages of scientific inquiry as described by Peirce My fellow passenger deplores the plebeian vulgarity of his congressman I frame the hypothesis that he is a mugwump I conclude that he is likely to oppose government regulation of business I ask him his opinion on a recent measure in restraint of trade, and my hypothesis is confirmed by his vehement denunciation It remains, however, no more than probable, in spite of further conversation, for the train journey is, mercifully, only finitely long The Saga of Principia Mathematica Peirce’s logical investigations left little mark on the development of logic in the early twentieth century It was rather the work of Frege that was carried forward, in particular by the work of Russell and Whitehead, his successors in the quest for the logicist grail The three volumes of Principia Mathematica contain a systematization of logic that soon became much better known than that presented in Frege’s own works One reason for the greater popularity of Principia is that it replaces Frege’s ingenious but cumbersome symbolism with a much more convenient notation, which Russell and Whitehead took over from its inventor, the Italian mathematician Giuseppe Peano Whereas Frege’s system was twodimensional, and called for complicated typesetting, the Peano system is linear, and calls only for a few special signs in addition to letters of the alphabet Thus the tilde sign ‘$’ was used for negation, the sign ‘V’ for disjunction, and the horseshoe sign ‘'’ for the truth-functional ‘if’ These 110