58 OF UNDISTURBED MOTION. 



that we oaDDot help concluding the stone's weight to be the 

 immediate and necessary cause of its fall, and that every 

 heavy body will fall unless supported ; and the pressure of 

 the string to be the necessary cause of the arrow's motion, 

 and that if we shoot, the arrow will fly ; and if we hesitated 

 to make these conclusions, we should often pay dear for 

 our scepticism. This explanation is suflicient to show the 

 identity of the two expressions, that "like causes produce 

 like effects," and that "in similar circumstances, similar 

 consequences ensue." And such is the ground of argument 

 from experience, the simplest principle of reasoning, after 

 pure mathematical truths ; which appear to be so far prior to 

 experience, as their contradiction always implies an absur- 

 dity repugnant to the imagination. 



Scholium 3. In the application of induction, the 

 greatest caution and circumspection are necessary ; for it 

 is obvious that, before we can infer with certainty the com- 

 plete similarity of two contingent events, we must be per- 

 fectly well assured that we are acquainted with every cir- 

 cumstance which can have any relation to their causes. 

 The error of some of the ancient schools consisted princi- 

 pally in the want of suflScient precaution in this respect ; 

 for although Bacon is, with great justice, considered as the 

 author of the most correct method of induction, yet, ac- 

 cording to his own statement, it was chiefly the guarded 

 and gradual appHcation of the mode of argument, that he 

 laboured to introduce. He remarks, that the Aristotelians, 

 from a hasty observation of a few concurring facts, pro- 

 ceeded immediately to deduce universal principles of 

 science, and fundamental laws of nature, and then derived 

 from these, by their syllogisms, all the particular cases, 

 which ought to have been made intermediate steps in the 

 inquiry. Of such an error we may easily find a familiar 



