A less strict species would be that in F, the size of P depends in some way on the size of one or more factors X, X, X, etc., each of the relevant factors being identical to one of the possible causes A, B, C, D, E. Again, if we find that P varies then that, for example. B A varies, but that B, C, D, E remain constant, this does not show that B, for example, cannot be identical to X, etc.; In other words, it does not show that B variations are not relevant to P. It only shows that the size of P does not depend entirely on a number of factors that do not include A, as each of these sets has remained constant while P has varied. This leaves open that the full cause of P could be in F itself, or some factors might be, such as (A, B, D), which also includes A and some of the others. All we know is that the A-list must be included. This observation and hypothesis therefore show that a complete cause of P in F (A, … ); That is, A is a really relevant factor and there may or may not be others. Repeated applications of this method may fill other factors, but not close the list.
(As has been the case so far, this is another task that needs to be done by another type of investigation to determine how the magnitude of P depends on those of the factors that have proved to be truly relevant.) Here, the D is eliminated because it is missing in I1 and is therefore not necessary, and B, C and E are eliminated because they are present in N1 and are therefore not sufficient. Assuming that one of the possible causes is necessary and sufficient for the F-in-F, it follows that this is the case. (Note that, since it wouldn`t matter if z.B E wasn`t present in I1, the presence of the actual cause in I1 should not be the only difference between instances.) We can point out here that the method of difference, unlike some variants of the agreement method, requires the assumption that there is a condition that is both necessary and sufficient for P. It is true, as we will see later for variants 4.2 and 8.2, that the “cause” identified by this method is often not itself a necessary or even sufficient condition; but it is necessary to assume that something is necessary and sufficient. So there will not be a method of agreement, a method of difference and a common method, but a number of variations of each. A full survey of all kinds of methods of this type, numbered as follows: A number of 1 to 8 before a decimal comma indicates the mode of adoption. It is therefore assumed that there is a real cause, that is, that the residue method can be interpreted as a variant of the differential method in which the negative instance is not observed, but built on the basis of already known causal laws. Knowledge expands when we can verify or distort a hypothesis.
This is because experimental tests are designed in such a way that the hypothesis is probably a general explanation of certain facts and not an isolated case.