4f OUTLINES OF NATURAL PHILOSOPHY. 



causes in these two systems are also similar, we are 

 said to reason from ANALOGY. 



Such reasonings will be more or less conclusive, ac- 

 cording as the similarity is more or less considerable. 

 Explanations; therefore, or theories founded on ana- 

 logy, may have all degrees of evidence, from the least 

 to the greatest. 



Many theories are founded entirely on analogy, 



10, When a theory has been discovered by in- 

 duction, it may be made use of by reasoning in a 

 reverse order, for discovering new facts, and pre- 

 dicting the result of new combinations. 



This will be best illustrated by the examples that will 

 occur in treating of Physical Astronomy. 



11. The evidence of a theory, increases with the 

 number of facts which it explains, and the preci- 

 sion with which it explains them. It diminishes 

 with the number of facts which it does not ex- 

 plain, and with the number of different supposi- 

 tions that will afford explanations equally pre- 

 cise. 



In the analytical OF inductive method of BACON, the 

 possible theories are all excluded but one or at most 

 a small number, before the explanation is attempt- 

 ed. Novum Organum, Lib. n. cap. 16. 



A theory may not deserve to be rejected, though it 

 does not explain all the phenomena, if it explain a 

 great number, and be not absolutely inconsistent 



with 



