282 PREFACE TO THE 



elements are not so? In this point of view the unpictu- 

 resqueness of symbolical language, though it has led to 

 other inconveniences, has delivered us from a great 

 deal of confused thinking. If Poinsot's illustration of 

 the motion of a rigid body by means of a central ellip- 

 soid rolling on a fixed plane, had been proposed at the 

 beginning of the seventeenth century, most people would 

 have said that the hypothesis was absurd, though it 

 might correspond to the phenomena. 



To take the matter more generally, it must be re- 

 membered that positive truth or falsehood belongs only 

 to the region of the actual and individuated. To say 

 that two and three make five is not to deny that four 

 and one do so too, although if I assert that of five 

 houses, first three were built and then two added, I 

 contradict the assertion that four were built at first 

 and that only one is of later date. Not merely in the 

 relation between cinematical or formal and physical 

 astronomy, but generally, the question whether an 

 hypothesis be true or false does not arise unless it is 

 presented as a causal explanation. Thus when Bero- 

 sus taught that one half of the moon is luminous, and 

 that her phases arise from this half being always turned 

 towards the sun in virtue of their mutual sympathy, 

 both being bright, the explanation is unexceptionable, 

 except so far as relates to the efficient cause. One 

 half of the moon always is bright ; and always is turned 

 to the sun ; and this Berosus saw as clearly as we do. 

 It is in this way that false hypotheses are transformed 

 into true ones ; not by the transformation of anything 

 false into truth, but by the severance of the causal or 

 real element from that which is neither true nor false, 

 namely the abstract conception. But the interest 



