Editing Deductive reasoning (section)

=== Definitory and strategic rules ===
Rules of inferences are definitory rules: they determine whether an argument is deductively valid or not. But reasoners are usually not just interested in making any kind of valid argument. Instead, they often have a specific point or conclusion that they wish to prove or refute. So given a set of premises, they are faced with the problem of choosing the relevant rules of inference for their deduction to arrive at their intended conclusion.<ref name="Hintikka" /><ref name="BritannicaSystems">{{Cite encyclopedia |title=Logical systems |encyclopedia=Encyclopædia Britannica |url=https://www.britannica.com/topic/logic/Logical-systems |access-date=4 December 2021}}</ref><ref name="Pedemonte">{{Cite journal |last=Pedemonte |first=Bettina |date=25 June 2018 |title=Strategic vs Definitory Rules: Their Role in Abductive Argumentation and their Relationship with Deductive Proof |url=https://www.ejmste.com/article/strategic-vs-definitory-rules-their-role-in-abductive-argumentation-and-their-relationship-with-5539 |journal=Eurasia Journal of Mathematics, Science and Technology Education |volume=14 |issue=9 |pages=em1589 |doi=10.29333/ejmste/92562 |issn=1305-8215 |s2cid=126245285 |doi-access=free}}</ref> This issue belongs to the field of strategic rules: the question of which inferences need to be drawn to support one's conclusion. The distinction between definitory and strategic rules is not exclusive to logic: it is also found in various games.<ref name="Hintikka" /><ref name="BritannicaSystems" /><ref name="Pedemonte" /> In [[chess]], for example, the definitory rules state that [[Bishop (chess)|bishops]] may only move diagonally while the strategic rules recommend that one should control the center and protect one's [[King (chess)|king]] if one intends to win. In this sense, definitory rules determine whether one plays chess or something else whereas strategic rules determine whether one is a good or a bad chess player.<ref name="Hintikka" /><ref name="BritannicaSystems" /> The same applies to deductive reasoning: to be an effective reasoner involves mastering both definitory and strategic rules.<ref name="Hintikka" />