Philosophy

=== Logic ===
{{Main|Logic}}

Logic is the study of [[Logical reasoning|correct reasoning]]. It aims to understand how to distinguish good from bad [[argument]]s.<ref>{{multiref |1={{harvnb|Hintikka|2019}} |2={{harvnb|Haack|1978|loc=Philosophy of Logics}} }}</ref> It is usually divided into formal and [[informal logic]]. Formal logic uses [[formal language|artificial languages]] with a precise symbolic representation to investigate arguments. In its search for exact criteria, it examines the structure of arguments to determine whether they are correct or incorrect. Informal logic uses non-formal criteria and standards to assess the correctness of arguments. It relies on additional factors such as content and context.<ref>{{multiref |1={{harvnb|Blair|Johnson|2000|pp=94–96}} |2={{harvnb|Walton|1996}} |3={{harvnb|Tully|2005|p=532}} |4={{harvnb|Johnson|1999|pp=265–267}} |5={{harvnb|Groarke|2021}} }}</ref>

Logic examines a variety of arguments. [[Deductive arguments]] are mainly studied by formal logic. An argument is deductively [[Validity (logic)|valid]] if the truth of its [[premise]]s ensures the truth of its conclusion. Deductively valid arguments follow a [[rule of inference]], like ''[[modus ponens]]'', which has the following [[logical form]]: "''p''; if ''p'' then ''q''; therefore ''q''". An example is the argument "today is Sunday; if today is Sunday then I don't have to go to work today; therefore I don't have to go to work today".<ref>{{multiref |1={{harvnb|Velleman|2006|pp=8, 103}} |2={{harvnb|Johnson-Laird|2009|pp=[https://wires.onlinelibrary.wiley.com/doi/abs/10.1002/wcs.20 8–10]}} |3={{harvnb|Dowden|2020|pp=334–336, 432}} }}</ref>

The premises of non-deductive arguments also support their conclusion, although this support does not guarantee that the conclusion is true.<ref>{{multiref |1={{harvnb|Dowden|2020|pp=432, 470}} |2={{harvnb|Anshakov|Gergely|2010|p=[https://books.google.com/books?id=OuyQgE_gf2QC&pg=PA128 128]}} }}</ref> One form is [[inductive reasoning]]. It starts from a set of individual cases and uses generalization to arrive at a universal law governing all cases. An example is the inference that "all ravens are black" based on observations of many individual black ravens.<ref>{{multiref |1={{harvnb|Vickers|2022}} |2={{harvnb|Nunes|2011|pp=[https://books.google.com/books?id=xZuSxo4JxoAC 2066–2069]|loc=Logical Reasoning and Learning}} |3={{harvnb|Dowden|2020|pp=432–449, 470}} }}</ref> Another form is [[abductive reasoning]]. It starts from an observation and concludes that the best explanation of this observation must be true. This happens, for example, when a doctor diagnoses a disease based on the observed symptoms.<ref>{{multiref |1={{harvnb|Douven|2022}} |2={{harvnb|Koslowski|2017|pp=366–368|loc=Abductive Reasoning and Explanation}} |3={{harvnb|Nunes|2011|pp=[https://books.google.com/books?id=xZuSxo4JxoAC 2066–2069]|loc=Logical Reasoning and Learning}} }}</ref>

Logic also investigates incorrect forms of reasoning. They are called ''[[fallacies]]'' and are divided into [[Formal fallacy|formal]] and [[informal fallacies]] based on whether the source of the error lies only in the form of the argument or also in its content and context.<ref>{{multiref |1={{harvnb|Hansen|2020}} |2={{harvnb|Dowden|2023}} |3={{harvnb|Dowden|2020|p=290}} |4={{harvnb|Vleet|2011|p=[https://books.google.com/books?id=UCFYUGRG5dcC&pg=PR9 ix]}} }}</ref>