FALLACIES OF OBSERVATION. 641 



multo freqnentius, tameu negligunt, et praetereunt." And he proceeds to 

 say that, independently of the love of the marvelous, or any other bias in 

 the inclinations, there is a natural tendency in the intellect itself to this 

 kind of fallacy ; since the mind is more moved by affirmative instances, 

 though negative ones are of most use in philosophy : " Is tamen humano 

 intellectui error est proprius et perpetuus, ut magis moveatur et excitetur 

 Affirmativis qnam Negativis; cum rite et ordine sequum se utrique prae- 

 bere debeat; quin contra, in omni Axiomate vero constituendo, major vis 

 est instantise negativas." 



But the greatest of all causes of non-observation is a preconceived opin- 

 ion. This it is which, in all ages, has made the whole race of mankind, 

 and every separate section of it, for the most part unobservant of all facts, 

 however abundant, even when passing under their own eyes, which are con- 

 tradictory to any first appearance, or any received tenet. It is worth 

 while to recall occasionally to the oblivious memory of mankind some of 

 the striking instances in which opinions that the simplest experiment 

 would have shown to be erroneous, continued to be entertained because 

 nobody ever thought of trying that experiment. One of the most remark- 

 able of these was exhibited in the Copernican controversy. The opponents 

 of Copernicus argued that the eai-th did not move, because if it did, a 

 stone let fall from the top of a high tower would not reach the ground at 

 the foot of the tower, but at a little distance from it, in a contrary direc- 

 tion to the earth's course ; in the same manner (said they) as, if a ball is 

 let drop from the mast-head while the ship is in full sail, it does not fall 

 exactly at the foot of the mast, but nearer to the stern of the vessel. The 

 Copernicans would have silenced these objectors at once if they had tried 

 dropping a ball from the mast-head, since they would have found that it 

 does fall exactly at the foot, as the theory requires ; but no ; they admitted 

 the spurious fact, and struggled vainly to make out a difference between 

 the two cases. "The ball was t[\o part of the ship — and the motion for- 

 ward was not natural, either to the ship or- to the ball. The'stone, on the 

 other hand, let fall from the top of the tower, was a part of the earth ; and 

 therefore, the diurnal and annular revolutions which were natttral to the 

 earth, were also natural to the stone; the stone would, thei-efore, retain 

 the same motion with the tower, and strike the ground precisely at the 

 bottom of it."* 



Other examples, scarcely less striking, are recorded by Dr. Whewell,f 

 where imaginary laws of nature have continued to be received as real, 

 merely because no person had steadily looked at facts which almost every 

 one had the opportunity of observing. "A vague and loose mode of look- 

 ing at facts very easily observable, left men for a long time under the be- 

 lief that a body ten times as heavy as another falls ten times as fast ; that 

 objects immersed in water are always magnified, without regard to the 

 form of the surface ; that the magnet exerts an irresistible force ; that crys- 

 tal is always found associated with ice; and the like. These and many 

 others are examples how blind and careless man can be even in observation 

 of the plainest and commonest appearances; and they show us that the 

 mere faculties of perception, although constantly exei'cised upon innumer- 

 able objects, may long fail in leading to any exact knowledge." 



If even on physical facts, and these of the most obvious character, the 

 observing faculties of mankind can be to this degree the passive slaves of 



* Play fair's Dissertation, sect. 4. t Nov. Org. Renov., p. 61. 



