39 6 BACON 



stock, agree in every respect but that of color. Thence we 

 easily deduce that color has not much to do with the intrinsic 

 natures of any body, but depends only on the coarser and as it 

 were mechanical arrangement of the parts. These are solitary 

 instances as regards difference. We call them both solitary or 

 wild, to borrow a word from the astronomers. 



23. In the second rank of prerogative instances we will 

 consider migrating instances. In these the required nature 

 passes towards generation, having no previous existence, or 

 towards corruption, having first existed. In each of these divi- 

 sions, therefore, the instances are always twofold, or rather it is 

 one instance, first in motion or on its passage, and then brought 

 to the opposite conclusion. These instances not only hasten and 

 confirm exclusion, but also reduce affirmation, or the form 

 itself, to a narrow compass ; for the form must be something 

 conferred by this migration, or, on the contrary, removed and 

 destroyed by it ; and although all exclusion advances affirma- 

 tion, yet this takes place more directly in the same than in dif- 

 ferent subjects ; but if the form (as it is quite clear from what 

 has been advanced) exhibit itself in one subject, it leads to all. 

 The more simple the migration is, the more valuable is the 

 instance. These migrating instances are, moreover, very use- 

 ful in practice, for since they manifest the form, coupled with 

 that which causes or destroys it, they point out the right practice 

 in some subjects, and thence there is an easy transition to those 

 with which they are most allied. There is, however, a degree 

 of danger which demands caution, namely, lest they should 

 refer the form too much to its efficient cause, and imbue, or at 

 least tinge, the understanding with a false notion of the form 

 from the appearance of such cause, which is never more than a 

 vehicle or conveyance of the form. This may easily be remedied 

 by a proper application of exclusion. 



Let us then give an example of a migrating instance. Let 

 whiteness be the required nature. An instance which passes 

 towards generation is glass in its entire and in its powdered 

 state, or water in its natural state, and when agitated to froth ; 

 for glass when entire, and water in its natural state, are trans- 

 parent and not white, but powdered glass and the froth of water 

 are white and not transparent. We must inquire, therefore, 

 what has happened to the glass or water in the course of this 

 migration ; for it is manifest that the form of whiteness is con- 

 veyed and introduced by the bruising of the glass and the agita- 

 tion of the water ; but nothing is found to have been introduced 

 put a Diminishing of the parts of the glass and water and the 

 insertion of air. Yet this is no slight progress towards dis- 

 covering the form of whiteness, namely, that two bodies, in 

 themselves more or less transparent (as air and water, or air and 



