To assess the strength of these criticisms and determine the true value of disposal methods, Mill`s formulation does not need to be discussed in detail. Instead, it is sufficient to determine what would be the valid demonstrative methods that correspond to Mills` classes, and then to ask whether such methods or approximations of them have a place in scientific or reasonable study. 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. Assuming the fourth type (whether the required condition is either a possible cause or a disjunction of possible causes), the negative method of agreement (4.13 and 4.14) works as in 1.13 and 1.14, but the positive method of agreement is now seriously affected. Indeed, in observation 1.12 given above, the necessary and sufficient condition, for example. B (B or C), for this disjunction could be available in both I1 and I2, although none of its disjunctions are included in both. The observation of 1.12 would therefore leave the result quite undecided. We need (for 4.12) a much stronger observation, that is, a single positive case where A is present, but where all other possible causes are absent together; but this too now shows only that the cause is (A or…). This hypothesis (that the cause may be a disjunction of potential causes) allows what Mill called a “plurality of causes” because each of the disjunctions is in itself a “cause” in the sense that it is a sufficient condition; And what we have just taken note of is how this possibility undermines the application of the agreement method. Finally, where such causal links are not the main focus of the investigation, we constantly use cause-and-effect links, particularly singular causal sequences.
By measuring, say, a voltage, we assume that it was the connection of the measuring device on the terminals that caused this distraction from its needle, and the precautions that make it really the case must be explained in relation to our methods. This reasoning illustrates Mill`s method of residues: many elements of a complex effect are demonstrated by reliable causal convictions from several elements of a complex cause; All that remains of the effect must have been produced by the remnants of the cause.