For a property to be a necessary condition, it must always be present when the effect is present. Since this is the case, we are interested in examining cases where the effect is present and to learning about the characteristics that exist and are absent under the “possible necessary conditions.” Obviously, the properties missing if the effect is present cannot be necessary conditions for effect. This method is also generally described in comparative policy as the most diverse conception of the system. Symbolically, the method of agreement can be presented as: perhaps the best way to introduce Mills` methods is an example. Suppose your family went to a buffet dinner together, but when you got home, you started to feel sick and feel stomach pains. How do you determine the cause of the disease? Suppose you create a table of foods that are taken by each member of the family: one of the main characteristics of the scientific methodology is verification and falsification. Remember J. 4 that an appeal is made to Dieun if we conclude for lack of evidence that something is the case or not. While there are times when a lack of evidence should lead to a judgment that the original claim is not substantiated (as in a criminal court), this is not the case in scientific practices.
Mills` methods are five methods of induction described by the philosopher John Stuart Mill in 1843 in his book A System of Logic.  They must shed light on issues of causation. Perhaps it is best to consider Mill`s methods more modestly than the tools we can use in our efforts to confirm assumptions about the natural world. If we have already made several specific hypotheses about what could be the cause of an observed event, the use of the methods will be useful, as it will often allow us to eliminate most of the possible causes we have identified, which tends to confirm the hypothesis that any remaining circumstance will likely be the real cause. Philosopher John Stuart Mill has developed a series of five methods (or canons) that analyze and interpret our observations in order to draw conclusions about the cause-and-effect relationships they have. This method is also generally known as the most similar system design in the context of comparative policy. Although Mills` methods are an important part of the serious study of natural phenomena, they have significant constraints. These methods can only be applied with care if all relevant pre-gonal circumstances are taken into account, which cannot be guaranteed in advance.
Thus, we might find that you felt a little sick after eating an oyster, while your sister was rather comfortable eating a few, and your father became seriously ill after eating ten in a row. Since the variation in the number of oysters corresponds to a variation in the severity of the disease, it would be reasonable to infer that the diseases were caused by oysters. Consider as an example of the two similar countries difference method. Country A has a centre-right government, a uniform system and was a former colony. Country B has a centre-right government, a single system, but has never been a colony. The difference between countries is that Country A easily supports anti-colonial initiatives, while country B does not. The difference method would or would not identify the independent variable as the status of each country as a former colony, the dependent variable supporting anticolonial initiatives.