{"id":2662,"date":"2022-03-29T22:16:55","date_gmt":"2022-03-29T22:16:55","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/chapter\/2-8-deductive-vs-inductive-arguments-2\/"},"modified":"2024-01-15T16:52:57","modified_gmt":"2024-01-15T16:52:57","slug":"2-8-deductive-vs-inductive-arguments-2","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/chapter\/2-8-deductive-vs-inductive-arguments-2\/","title":{"raw":"2.8 Deductive vs. Inductive arguments","rendered":"2.8 Deductive vs. Inductive arguments"},"content":{"raw":"<div class=\"textbox shaded\">\r\n\r\n<strong>LEARNING OBJECTIVES<\/strong>\r\n\r\n<hr \/>\r\n\r\nBy the end of this section you will discover:\r\n<ul>\r\n \t<li>The difference between deductive and inductive arguments.<\/li>\r\n<\/ul>\r\n<\/div>\r\nThe concepts of validity and soundness that we have introduced apply only to the class of what are called \u201cdeductive arguments\u201d. A <strong>deductive argument<\/strong> is an argument whose conclusion is supposed to follow from its premises with absolute <strong>certainty<\/strong>, thus leaving no possibility that the conclusion does not follow from the premises.\r\n<div class=\"textbox shaded\"><strong>Deductive Argument<\/strong>: an argument whose conclusion is supposed to follow from its premises with absolute certainty<\/div>\r\nFor a deductive argument to fail to do this is for it to fail as a deductive argument.\r\n\r\nIn contrast, an <strong>inductive argument<\/strong> is an argument whose conclusion is supposed to follow from its premises with a high level of\u00a0probability, which means that although it is possible that the conclusion does not follow from its premises, it is unlikely that this is the case.\r\n<div class=\"textbox shaded\"><strong>Inductive Argument:<\/strong> an argument whose conclusion is supposed to follow from its premises with a high level of probability<\/div>\r\nThis video should help you understand the differences.\r\n<p style=\"text-align: center;\"><span style=\"text-decoration: underline;\"><strong>How to Argue - Introduction &amp; Abduction: Crash Course Philosophy #3\u00a0<\/strong><\/span><\/p>\r\n[embed]https:\/\/www.youtube.com\/embed\/-wrCpLJ1XAw[\/embed]\r\n<p style=\"text-align: center;\"><a href=\"https:\/\/youtu.be\/-wrCpLJ1XAw\" target=\"_blank\" rel=\"noopener noreferrer\">Or watch the video here<\/a><\/p>\r\n&nbsp;\r\n<table class=\"lines\" style=\"border-collapse: collapse; width: 100%; height: 75px;\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 15px;\">\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><\/td>\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>DEDUCTIVE REASONING<\/strong><\/td>\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>INDUCTIVE REASONING<\/strong><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px;\">\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Premises<\/strong><\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">Stated as facts or general <strong>principles<\/strong> (\"All crows are black\")<\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">Statements from <strong>observations<\/strong> of specific instances (\"The crow on my clothesline is black\")<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px;\">\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Conclusion<\/strong><\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are arranged logically, the conclusion offers <strong>certain<\/strong> knowledge<\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are compelling the conclusion can lead to a <strong>probable<\/strong> hypothesis, but never certainty<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px;\">\r\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Validity<\/strong><\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are true the conclusion is guaranteed true<\/td>\r\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are true the conclusion is probably true<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nHere is an example of an inductive argument:\r\n<div class=\"textbox shaded\">Tweets is a healthy, normally functioning bird and since most healthy, normally functioning birds fly, Tweets probably flies.<\/div>\r\nNotice that the conclusion, Tweets probably flies, contains the word \u201cprobably.\u201d This is a clear indicator that the argument is supposed to be inductive, not deductive. Here is the argument in standard form:\r\n<div class=\"textbox shaded\">\r\n<ol>\r\n \t<li>Tweets is a healthy, normally functioning bird<\/li>\r\n \t<li>Most healthy, normally functioning birds fly<\/li>\r\n \t<li>Therefore, Tweets probably flies<\/li>\r\n<\/ol>\r\n<\/div>\r\nGiven the information provided by the premises, the conclusion does seem to be well supported. That is, the premises do give us a strong reason for accepting the conclusion. This is true even though we can imagine a scenario in which the premises are true and yet the conclusion is false. For example, suppose that we added the following premise:\r\n<div class=\"textbox shaded\">Tweets is 6 ft tall and can run 30 mph.<\/div>\r\nWere we to add that premise, the conclusion would no longer be supported by the premises, since any bird that is 6 ft tall and can run 30 mph, is not a kind of bird that can fly. That information leads us to believe that Tweets is an ostrich or emu, which are not kinds of birds that can fly. As this example shows, inductive arguments are defeasible arguments since by adding further information or premises to the argument, we can overturn (defeat) the verdict that the conclusion is well-supported by the premises. Inductive arguments\u2014whose premises give us a strong, even if defeasible, reason for accepting the conclusion\u2014 are called, unsurprisingly, strong inductive arguments. In contrast, an inductive argument that does not provide a strong reason for accepting the conclusion are called weak inductive arguments.\r\n\r\nWhereas strong inductive arguments are defeasible, valid deductive arguments are not. Suppose that instead of saying that <em>most<\/em> birds fly, premise 2 said that <em>all<\/em> birds fly.\r\n<div class=\"textbox shaded\">\r\n<ol>\r\n \t<li>Tweets is a healthy, normally function bird.<\/li>\r\n \t<li>All healthy, normally functioning birds can fly.<\/li>\r\n \t<li>Therefore, Tweets can fly.<\/li>\r\n<\/ol>\r\n<\/div>\r\nThis is a valid argument and since it is a valid argument, there are no further premises that we could add that could overturn the argument\u2019s validity. (True, premise 2 is false, but as we have seen that is irrelevant to determining whether an argument is valid.) Even if we were to add the premise that Tweets is 6 ft tall and can run 30 mph, it does not overturn the validity of the argument. As soon as we use the universal generalization, \u201c<em>all<\/em> healthy, normally function birds can fly,\u201d then when we assume that premise is true and add that Tweets is a healthy, normally functioning bird, it <em>has<\/em> to follow from those premises that Tweets can fly. This is true even if we add that Tweets is 6 ft tall because then what we have to imagine (in applying our informal test of validity) is a world in which all birds, including those that are 6 ft tall and can run 30 mph, can fly.\r\n\r\nAlthough inductive arguments are an important class of argument that are commonly used every day in many contexts, logic texts tend not to spend as much time with them since we have not agreed upon standard of evaluating them. In contrast, there is an agreed upon standard of evaluation of deductive arguments. We have already seen what that is; it is the concept of validity. In chapter 2 we will learn some precise, formal methods of evaluating deductive arguments. There are no such agreed upon formal methods of evaluation for inductive arguments. This is an area of ongoing research in philosophy. In chapter 3 we will revisit inductive arguments and consider some ways to evaluate inductive arguments.\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n<p style=\"text-align: center;\"><strong>Works Cited<\/strong><\/p>\r\n<p class=\"hanging-indent\">CrashCourse, director. <i>How to Argue - Induction &amp; Abduction: Crash Course Philosophy #3<\/i>. <i>YouTube<\/i>, YouTube, 22 Feb. 2016, https:\/\/youtu.be\/-wrCpLJ1XAw<\/p>","rendered":"<div class=\"textbox shaded\">\n<p><strong>LEARNING OBJECTIVES<\/strong><\/p>\n<hr \/>\n<p>By the end of this section you will discover:<\/p>\n<ul>\n<li>The difference between deductive and inductive arguments.<\/li>\n<\/ul>\n<\/div>\n<p>The concepts of validity and soundness that we have introduced apply only to the class of what are called \u201cdeductive arguments\u201d. A <strong>deductive argument<\/strong> is an argument whose conclusion is supposed to follow from its premises with absolute <strong>certainty<\/strong>, thus leaving no possibility that the conclusion does not follow from the premises.<\/p>\n<div class=\"textbox shaded\"><strong>Deductive Argument<\/strong>: an argument whose conclusion is supposed to follow from its premises with absolute certainty<\/div>\n<p>For a deductive argument to fail to do this is for it to fail as a deductive argument.<\/p>\n<p>In contrast, an <strong>inductive argument<\/strong> is an argument whose conclusion is supposed to follow from its premises with a high level of\u00a0probability, which means that although it is possible that the conclusion does not follow from its premises, it is unlikely that this is the case.<\/p>\n<div class=\"textbox shaded\"><strong>Inductive Argument:<\/strong> an argument whose conclusion is supposed to follow from its premises with a high level of probability<\/div>\n<p>This video should help you understand the differences.<\/p>\n<p style=\"text-align: center;\"><span style=\"text-decoration: underline;\"><strong>How to Argue &#8211; Introduction &amp; Abduction: Crash Course Philosophy #3\u00a0<\/strong><\/span><\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"How to Argue - Induction &amp; Abduction: Crash Course Philosophy #3\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/-wrCpLJ1XAw?feature=oembed&#38;rel=0&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/youtu.be\/-wrCpLJ1XAw\" target=\"_blank\" rel=\"noopener noreferrer\">Or watch the video here<\/a><\/p>\n<p>&nbsp;<\/p>\n<table class=\"lines\" style=\"border-collapse: collapse; width: 100%; height: 75px;\">\n<tbody>\n<tr style=\"height: 15px;\">\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><\/td>\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>DEDUCTIVE REASONING<\/strong><\/td>\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>INDUCTIVE REASONING<\/strong><\/td>\n<\/tr>\n<tr style=\"height: 15px;\">\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Premises<\/strong><\/td>\n<td style=\"width: 33.3333%; height: 15px;\">Stated as facts or general <strong>principles<\/strong> (&#8220;All crows are black&#8221;)<\/td>\n<td style=\"width: 33.3333%; height: 15px;\">Statements from <strong>observations<\/strong> of specific instances (&#8220;The crow on my clothesline is black&#8221;)<\/td>\n<\/tr>\n<tr style=\"height: 15px;\">\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Conclusion<\/strong><\/td>\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are arranged logically, the conclusion offers <strong>certain<\/strong> knowledge<\/td>\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are compelling the conclusion can lead to a <strong>probable<\/strong> hypothesis, but never certainty<\/td>\n<\/tr>\n<tr style=\"height: 15px;\">\n<td class=\"shaded\" style=\"width: 33.3333%; height: 15px;\"><strong>Validity<\/strong><\/td>\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are true the conclusion is guaranteed true<\/td>\n<td style=\"width: 33.3333%; height: 15px;\">If the premises are true the conclusion is probably true<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Here is an example of an inductive argument:<\/p>\n<div class=\"textbox shaded\">Tweets is a healthy, normally functioning bird and since most healthy, normally functioning birds fly, Tweets probably flies.<\/div>\n<p>Notice that the conclusion, Tweets probably flies, contains the word \u201cprobably.\u201d This is a clear indicator that the argument is supposed to be inductive, not deductive. Here is the argument in standard form:<\/p>\n<div class=\"textbox shaded\">\n<ol>\n<li>Tweets is a healthy, normally functioning bird<\/li>\n<li>Most healthy, normally functioning birds fly<\/li>\n<li>Therefore, Tweets probably flies<\/li>\n<\/ol>\n<\/div>\n<p>Given the information provided by the premises, the conclusion does seem to be well supported. That is, the premises do give us a strong reason for accepting the conclusion. This is true even though we can imagine a scenario in which the premises are true and yet the conclusion is false. For example, suppose that we added the following premise:<\/p>\n<div class=\"textbox shaded\">Tweets is 6 ft tall and can run 30 mph.<\/div>\n<p>Were we to add that premise, the conclusion would no longer be supported by the premises, since any bird that is 6 ft tall and can run 30 mph, is not a kind of bird that can fly. That information leads us to believe that Tweets is an ostrich or emu, which are not kinds of birds that can fly. As this example shows, inductive arguments are defeasible arguments since by adding further information or premises to the argument, we can overturn (defeat) the verdict that the conclusion is well-supported by the premises. Inductive arguments\u2014whose premises give us a strong, even if defeasible, reason for accepting the conclusion\u2014 are called, unsurprisingly, strong inductive arguments. In contrast, an inductive argument that does not provide a strong reason for accepting the conclusion are called weak inductive arguments.<\/p>\n<p>Whereas strong inductive arguments are defeasible, valid deductive arguments are not. Suppose that instead of saying that <em>most<\/em> birds fly, premise 2 said that <em>all<\/em> birds fly.<\/p>\n<div class=\"textbox shaded\">\n<ol>\n<li>Tweets is a healthy, normally function bird.<\/li>\n<li>All healthy, normally functioning birds can fly.<\/li>\n<li>Therefore, Tweets can fly.<\/li>\n<\/ol>\n<\/div>\n<p>This is a valid argument and since it is a valid argument, there are no further premises that we could add that could overturn the argument\u2019s validity. (True, premise 2 is false, but as we have seen that is irrelevant to determining whether an argument is valid.) Even if we were to add the premise that Tweets is 6 ft tall and can run 30 mph, it does not overturn the validity of the argument. As soon as we use the universal generalization, \u201c<em>all<\/em> healthy, normally function birds can fly,\u201d then when we assume that premise is true and add that Tweets is a healthy, normally functioning bird, it <em>has<\/em> to follow from those premises that Tweets can fly. This is true even if we add that Tweets is 6 ft tall because then what we have to imagine (in applying our informal test of validity) is a world in which all birds, including those that are 6 ft tall and can run 30 mph, can fly.<\/p>\n<p>Although inductive arguments are an important class of argument that are commonly used every day in many contexts, logic texts tend not to spend as much time with them since we have not agreed upon standard of evaluating them. In contrast, there is an agreed upon standard of evaluation of deductive arguments. We have already seen what that is; it is the concept of validity. In chapter 2 we will learn some precise, formal methods of evaluating deductive arguments. There are no such agreed upon formal methods of evaluation for inductive arguments. This is an area of ongoing research in philosophy. In chapter 3 we will revisit inductive arguments and consider some ways to evaluate inductive arguments.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><strong>Works Cited<\/strong><\/p>\n<p class=\"hanging-indent\">CrashCourse, director. <i>How to Argue &#8211; Induction &amp; Abduction: Crash Course Philosophy #3<\/i>. <i>YouTube<\/i>, YouTube, 22 Feb. 2016, https:\/\/youtu.be\/-wrCpLJ1XAw<\/p>\n","protected":false},"author":101,"menu_order":8,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":"cc-by-nc"},"chapter-type":[48],"contributor":[62,63],"license":[55],"class_list":["post-2662","chapter","type-chapter","status-publish","hentry","chapter-type-numberless","contributor-daniel-g-shaw","contributor-ph-d","license-cc-by-nc"],"part":2643,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapters\/2662","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/wp\/v2\/users\/101"}],"version-history":[{"count":2,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapters\/2662\/revisions"}],"predecessor-version":[{"id":2902,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapters\/2662\/revisions\/2902"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/parts\/2643"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapters\/2662\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/wp\/v2\/media?parent=2662"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/pressbooks\/v2\/chapter-type?post=2662"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/wp\/v2\/contributor?post=2662"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/introtophilosophy\/wp-json\/wp\/v2\/license?post=2662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}