502 LAPLACE. 



theory of probabilities is that it teaches us to mistrust our first 

 impressions; this is ilkistratecl by the example which we have 

 noticed in Art. 85G, and by the case of the Chevaher de Mere: 

 see Art. 10. Laplace makes on his page cviii. some remarks re- 

 specting the excess of the births of boys over the births of girls; 

 these remarks are new in the third edition. 



Laplace places in the list of illusions an application of the 

 Theory of Probability to the summation of series, which was 

 made by Leibnitz and Daniel BernoulK. They estimated the 



infinite series 



1-1+1-1 + .. . 



as equal to ^ ; because if we take an even number of terms we 



Jit 



obtain 0, and if we take an odd number of terms we obtain 1, 

 and they assumed it to be equally probable that an infinite 

 number of terms is odd or even. See Dugald Stewarfs Works 

 edited hy Hamilton, Vol. IV. page 204. 



Laplace makes some remarks on the apparent verification 

 which occasionally happens of predictions or of dreams; and justly 

 remarks that persons who attach importance to such coincidences 

 generally lose sight of the number of cases in which such antici- 

 pations of the future are falsified by the event. He says, 



Ainsi, le pliilosophe de Tantiqiiite, auqiiel on montrait dans un 

 temple, pour exalter la puissance du dieu qu'on y adorait, les ex voto 

 de tons cenx qui apres I'avoir invoqiie, s'etaient sauves du naufi^age, fit 

 une remarque conforme au calcul des prohabilites, en observant qu'il 

 ne voyait point inscrits, les noms de ceux qui, malgre cette invocation, 

 avaient peri. 



944. A long discussion on what Laplace calls Psycliologie 

 occupies pages cxiii — cxxviii of the present section. There is 

 much about the sensorium, and from the close of the discussion it 

 would appear that Laplace fancied all mental phenomena ought 

 to be explained by applying the laws of Dynamics to the vibra- 

 tions of the sensorium. Indeed we are told on page cxxiv. that 

 faith is a modification of the sensorium, and an extract from 

 Pascal is used in a manner that its author would scarcely have 

 approved. 



