NOVUM ORGANUM 187 



For example: let the required nature be heat. Flame 

 is an accompanying instance ; for in water, air, stone, metal, 

 and many other substances, heat is variable, and can ap 

 proach or retire; but all flame is hot, so that heat always 

 accompanies the concretion of flame. We have no hostile 

 instance of heat; for the senses are unacquainted with the 

 interior of the earth, and there is no concretion of any 

 known body which is not susceptible of heat. 



Again, let solidity be the required nature. Air is a 

 hostile instance; for metals may be liquid or solid, so may 

 glass ; even water may become solid by congelation, but air 

 cannot become solid or lose its fluidity. 



With regard to these instances of fixed propositions, 

 there are two points to be observed, which are of impor 

 tance. First, that if there be no universal affirmative or 

 negative, it be carefully noted as not existing. Thus, in 

 heat, we have observed that there exists no universal nega 

 tive, in such substances, at least, as have come to our 

 knowledge. Again, if the required nature be eternity or 

 incorruptibility, we have no universal affirmative within 

 our sphere, for these qualities cannot be predicated of any 

 bodies below the heavens, or above the interior of the earth. 

 Secondly, to our general propositions as to any concrete, 

 whether affirmative or negative, we should subjoin the 

 concretes which appear to approach nearest to the non- 

 existing substances; such as the most gentle or least- 

 burning flames in heat, or gold in incorruptibility, since it 

 approaches nearest to it. For they all serve to show the 

 limit of existence and non-existence, and circumscribe 

 forms, so that they cannot wander beyond the conditions 

 of matter. 



XXXIV. In the twelfth rank of prerogative instances, 



