178 NOVUM ORGANUM 



for instance, is toward the boundary of heaven, and that of 

 the nature of heat toward the centre of the earth, by a 

 similar species of opposition or rejection of the contrary 

 nature. 



Lastly, in the axioms of the sciences, there is a similarity 

 of instances worthy of observation. Thus the rhetorical 

 trope which is called surprise, is similar to that of music 

 termed the declining of a cadence. Again the mathe 

 matical postulate, that things which are equal to the same 

 are equal to one another, is similar to the form of the syl 

 logism in logic, which unites things agreeing in the middle 

 term. 50 Lastly, a certain degree of sagacity in collecting 

 and searching for physical points of similarity, is very use 

 ful in many respects. 61 



XXVIII. In the seventh rank of prerogative instances, 

 we will place singular instances, which we are also wont to 

 call irregular or heteroclite (to brorrow a term from the 

 grammarians). They are such as exhibit bodies in the con- 



50 Bacon falls into an error here in regarding the syllogism as something 

 distinct from the reasoning faculty, and only one of its forms. It is not gen 

 erally true that the syllogism is only a form of reasoning by which we unite 

 ideas which accord with the middle term. This agreement is not even essen 

 tial to accurate syllogisms; when .the relation of the two things compared to 

 the third is one of equality or similitude, it of course follows that, the two 

 things compared may be pronounced equal, or like to each other. But if the 

 relation between these terms exist in a different form, then it is not true that 

 the two extremes stand in the same relation to each other as to the middle 

 term. For instance, if A is double of B, and B double of c, then A is quadruple 

 of c. But then the relation of A to c is different from that of A to B and 

 of B to c. Ed. 



61 Comparative anatomy is full of analogies of this kind. Those between 

 natural and artificial productions are well worthy of attention, and sometimes 

 lead to important discoveries. By observing an analogy of this kind between 

 the plan used in hydraulic engines for preventing the counter-current of a fluid, 

 and a similar contrivance in the blood vessels, Harvey was led to the discovery 

 of the circulation of the blood. Ed. 



