54 o THE POPULAR SCIENCE MONTHLY. 



of certain stars at the birth of a child is, by the superstitious, said to 

 bode good or evil. If a new piece of work be commenced while the 

 moon is on the wane, or on a Friday, the undertaking is doomed to 

 fail. The belief in good and evil omens has survived thousands of 

 years, and has come down to the present day ; in fact, the influence 

 which this belief has on the mind can only be shaken off by calm rea- 

 soning and self -training. Many other instances of superstition, still in 

 vogue in our enlightened times, might readily be given. 



All of these are false conclusions derived in the same manner : post 

 hoc, ergo propter hoc (after it, therefore because of it). A careful com- 

 parison of different cases is not undertaken, no close scrutiny or in- 

 vestigation is attempted, no distinction made between essential and 

 non-essential conditions. In each case a general assertion is based on 

 a few separate, consecutive facts ; the relation between cause and effect 

 can not be proved in any instance. In fact, if we except the example 

 of quack-medicines cited, in all other cases, even the most vivid imagi- 

 nation will fail to cast a bridge be it ever so frail over the chasm 

 that separates what has preceded from the seeming effect. In short, 

 many prophecies that can be found and met with every day among the 

 people, in newspaper advertisements, etc., are replete with error, and 

 wholly unreliable. It is, then, not surprising that one comes to regard 

 all predictions skeptically ; in fact, one is entirely justified in looking 

 upon at least nine tenths of them with suspicion. 



The true observer will not rest content with the mere word " ex- 

 periment," a term so universally used. If one comes to look into mat- 

 ters closely, it will nearly always be found to refer to mere enumera- 

 tion. Rarely has a word been more misused than this one, " experi- 

 ment." Science has found a more adequate expression, and terms it 

 " induction." Induction is the means of discovering and proving gen- 

 eral propositions. This simple definition should be remembered. 



The best-known form of induction is Bacon's method by simple 

 enumeration. Can this method be successfully applied to formulate 

 predictions ? Many scholars consider this way of going to work en- 

 tirely useless for the ascertaining of truths. " Of what use can it be," 

 they say, " to know that a certain phenomenon has taken place a hun- 

 dred times ? Does that afford any guarantee that it must take place 

 again ? Or, even granting that it may happen once more, can not the 

 time come when it will not occur ? " 



Hence, induction by simple enumeration does not seem to be 

 adapted to the finding of general truths, such as science demands, 

 and in consequence does not seem serviceable as a means of securing 

 definite predictions. In fact, induction applied without the necessary 

 caution is the most crude and deceptive means of arriving at general 

 truths, and gives rise to innumerable false conclusions ; and yet we 

 owe to this inadequate method some important empirical generaliza- 

 tions. 



