Symbolically, the common method of correspondence and difference can be represented: the philosopher John Stuart Mill developed a series of five meticulous methods (or canons) that make it possible to analyze and interpret our observations to draw conclusions about the causal links they present. Determining exact cause and effect is not an easy task. We can often confuse them or misinterpret them because we lack sufficient information. Mill`s methods are attempts to isolate a cause from a complex sequence of events. The accompanying variation method with statistical methods that can be considered as work, is used in a large number of experimental studies where a potentially relevant factor is variable (everything that might be relevant is kept constant) to see if there is a causal link between this single factor and the effect in question. (Of course, what we consider a single experiment may include the variation of several factors, but always in such a way that the results show the effects of the variation of each factor for themselves: such an experiment is only a combination of several applications of simultaneous variation.) This principle, which is simply called the “common method”, simply represents the application of compliance and difference methods. With the hypothesis of the second species (that the required condition is either a possible cause or a negation of a possible cause), we need further observations. Therefore, for the variants of the positive method of conformity (2.11 and 2.12), we need the following: two or more positive instances, so that there is a possible cause (or negation), say A, in any case, but for any other possible cause, there is a instance in which it is present and a instance where it is absent. This is necessary to exclude, as a candidate for the role of the necessary (or necessary and sufficient) condition, possible negations and possible causes, with the exception of A itself. Mill`s methods should come as no surprise, as these rules articulate some of the principles we implicitly use in cause-and-effect reasoning in everyday life.
However, it is important to respect the limits of these rules. The residual method can be interpreted as a variant of the difference method in which the negative instance is not observed but constructed on the basis of already known laws of causality. In this particular case, you are the only one who has not fallen ill. The only difference between you and others is that you didn`t eat a salad. This is probably the cause of other people`s illnesses. This is an application of the method of difference. This rule states that if you have a situation that has one effect, and another that does not, and the only difference is the presence of a single factor in the first situation, we can deduce this factor as the cause of the effect. Third, although descriptions of eliminative induction methods have often been associated with a kind of empiricism level that treats knowledge as entirely related to empirical relationships between things, qualities, and directly observable processes, the methods themselves are not related to this doctrine, but can establish cause-and-effect relationships between entities that are indirectly observed. For example, as long as there is a direct or indirect possibility of determining when a magnetic field is present and when an electric current is in a wire, methods can determine whether such a current produces a magnetic field. For the simplest variant of the differential method (1.2), we need this observation: a positive instance I1 and a negative instance N1, so that among the possible causes present in I1, one, say A, is absent from N1, but the rest is present in N1.
For example, the corresponding variant (3.2) of the differential method requires only the observation of 1.2; but it only concludes that (A.) is a necessary and sufficient condition from P to F. . .