Ixxxvi INTRODUCTION 



nerve, an exact image of the fish which caused the sensation. 

 On this theory, therefore, the hemispheres become a vast 

 storehouse of miniature engravings, containing all the ideas 

 which the individual has ever formed. 



Let not the reader too hastily deride this fantastic specula- 

 tion. Its difficulties, and indeed absurdities, are in our day 

 so obvious that it is hard to remember that they were 

 not always obvious. Nearly all Lamarck's errors may be 

 matched by similar errors current at the present day, and 

 not always confined to vulgar people. His present error is 

 no exception. It is not uncommon to hear people of passable 

 education exhibiting exactly the same ignorance as to the 

 relations of the physical and the psychical. An external 

 object, at which we look, forms an image on the retina : 

 and since the light has to pass through the lens, the image 

 is inverted. Now it is quite a common thing to hear people 

 wondering how the inverted image on the retina can give 

 rise to an optical sensation of the object as being right 

 way up. It is even said very often that we do see 

 the object upside down, and rectify it unconsciously and 

 automatically. 



Now people who argue thus, or who see any unusual 

 difficulty in the matter, are in no better case than Lamarck 

 was a century ago, with his engravings in cavities of the 

 cerebral cortex. In each case, the psychical image is con- 

 fused with a physical image of the object : and whatever 

 the relation of psychical to physical may be, it is certainly 

 infinitely different from any such elementary analogy as 

 the above. Both illustrate that vicious tendency to hypo- 

 statisation, or manufacture of spiritual, material, or spirito- 

 material entities, which I have already so often endeavoured 

 to stigmatise. 



Lamarck was a follower of Locke and the empirical school. 

 He believed that all ideas were acquired, and that there 

 were no such things as innate ideas. Since he traced all 

 intellect to ideas, and all ideas to sensations, he must be 

 reckoned as a sensationalist ; probably he was influenced by 



