PHILOSOPHY, THE GUIDE OF MENTAL LIFE 261 



nuclear disintegration, neither matter nor energy is destroyed. 

 The atomic nucleus apparently breaks up into smaller material 

 units, most of which have high velocities and some of which have 

 "negligible" masses. We continue to grope our way toward the 

 demonstration of ever smaller material units. 



Our senses operate by and through particulate units, and we are 

 fortunate that certain threshold values of excitation must be 

 reached before an effect is registered on our consciousness. It is a 

 great protection to our nervous system that we cannot hear every 

 sound, no matter how faint; but we can use microphones to am- 

 plify these sounds when we wish. The rushing circulation of the 

 blood is not noticed by normal persons, but when the nerves are 

 supersensitive it may be felt as a "thrilling" or "tingling." 



Physical measurements are made by our senses, often assisted 

 or fortified by some kind of apparatus. Most apparatus is so 

 constructed as to outline a result on some visible graph or scale, 

 whereon height, inflections, cusps, rate of change, etc., become 

 visible and recordable. We thus avoid grave difficulties which 

 are likely to appear if we rely solely upon the unaided senses of 

 sight, taste, touch, smell or hearing. Thus among the 70 per cent 

 to whom phenyl thiocarbamide has any taste at all, some will find 

 it sour, others bitter, others sweet — and these idiosyncrasies are 

 heritable as Mendelian recessives. There is a real basis for the 

 old Latin maxim de gustibus non est disputandum. Most human 

 ears are deaf to sound vibrations in excess of about 20,000 per 

 second; but mice can hear supersonics far beyond the human 

 range. Bats ("bald mice" in French, and "flying mice" in German) 

 guide themselves in dark caves by sensing the reflections from the 

 walls of the supersonic squeaks they emit during flight. 



The thimble-rigger,* the three-card monte man,* the pick- 

 pocket, and the magician, all know that the hand is quicker than 

 the eye; and the many optical illusions known to psychologists 

 show how careful we must be before assuming that seeing is be- 



* The following definitions (Standard Dictionary) are for the benefit of guileless 

 mathematicians, who are not always the calculating persons some might imagine: 



Thimble-rig: A gambling game in which three thimble-shaped cups are placed 

 upside down on a board with a pea or ball under one of them, and shifted about 

 by sleight-of-hand, the aim being to induce bystanders to bet under which cup the 

 pea or ball is; frequently played at race-tracks, fairs, etc., in a swindling manner. 



Three-card monte: A sleight-of-hand game or trick played with three cards, one 

 of which is usually a court-card, in such a manner as to deceive the eye of the 

 onlooker, who is induced to bet that he can pick out the court-card. Called in 

 England three-card trick. 



