§ 5. The Canon Of Residues.
Subduct from any phenomenon such part as previous inductions have shown to be the effect of certain antecedents, and the residue of the phenomenon is the effect of the remaining antecedents.
The phenomenon is here assumed to be an effect: a similar Canon may be framed for residuary causes.
This also is not a fresh method, but a special case of the method of Difference. For if we suppose the phenomenon to be p q r, and the antecedent to be A B C, and that we already know B and C to have (either severally or together) the consequents q r, in which their efficacy is exhausted; we may regard
| B | C |
| q | r |
as an instance of the absence of p obtained deductively from the whole phenomenon
| A | B | C |
| p | q | r |
by our knowledge of the laws of B and C; so that
| A | B | C |
| p | q | r |
is an instance of the presence of p, differing otherwise from