The regress problem arises because a prior principle is required to explain logical principles, here modus ponens, and once "that" principle is explained, "another" principle is required to explain "that" principle. Thus, if the causal chain is to continue, the argument falls into infinite regress. However, if a formal system is introduced where modus ponens is simply a rule of inference defined within the system, then it can be abided by simply by reasoning within the system. In analogy, chess is played according to a particular set of rules, and when a person plays chess, he cannot question or beg to differ from the given rules, but must instead abide by them because they form the very framework of the game. That is not to say that the chess player agrees with these rules (consider for example, rule changes such as "en passant"). Likewise, a formal system of logic consists of inference rules that are to be followed by the user of the system, and when a person reasons according to this formal system, he cannot question or differ from these inference rules, but must instead abide by them because they form the very constituents of the system. That is not to say that the user reasoning according to this formal system agrees with these rules (consider for example, the constructivist's rejection of the Law of the Excluded Middle and the dialethist's rejection of the Law of noncontradiction). In this way, formalising logic as a system can be considered as a response to the problem of infinite regress: "modus ponens" is placed as a rule within the system, the validity of "modus ponens" is eschewed to without the system.