{"id":114151,"date":"2012-12-13T00:45:00","date_gmt":"2012-12-13T00:45:00","guid":{"rendered":"https:\/\/rockcontent.com\/?p=114151"},"modified":"2025-09-15T13:48:58","modified_gmt":"2025-09-15T16:48:58","slug":"logical-validity-v-soundness","status":"publish","type":"post","link":"https:\/\/pingback.com\/en\/resources\/logical-validity-v-soundness\/","title":{"rendered":"Logical Validity v. Soundness"},"content":{"rendered":"

The word logic is derived from the Greek word logos<\/em>. Logos<\/em> has several nuanced meanings, but the one with which I am presently concerned pertains to deductive argument. Logic is simply the rules by which one must abide in order to present a valid, deductive argument and nothing more. In the political environment in which we live, one in which the vicious polemic<\/a> is king, this is sometimes forgotten. However, logic is of paramount importance to anyone either looking to hire a blogger<\/a> or hoping to be hired as a blogger. Deductive reasoning is what distinguishes a thoughtful post from a derelict jeremiad.<\/p>\n

Deductive Validity<\/strong><\/p>\n

Arguments are made up of premises and conclusions. By using the basic rules of logic, one follows the premises of an argument in order to arrive at a conclusion. When the rules are followed, the argument is valid. Put in the overly formal language of my old textbook, \u201cThe Logic Book\u201d:<\/p>\n

An argument is deductively valid<\/em> if and only if it is not possible for the premises to be true and the conclusion false. An argument is deductively invalid<\/em> if and only if it is not deductively valid. (p. 11)<\/p>\n

For example, if Max is taller than Sandy, and Sandy is taller than Bill, then Max is taller than Bill. It can just as easily be thought of in numbers. Think of Max as 3, Sandy as 2 and Bill as 1.<\/p>\n

3 is greater than 2.<\/em><\/p>\n

2 is less than 3 and greater than 1.<\/em><\/p>\n

3 is, therefore, greater than 1.<\/em><\/p>\n

If this sounds a lot like geometry, then you\u2019re getting the message loud and clear. From the days of Euclid and Pythagoras up until today, logic, geometry and mathematics have been known to be inalienable from one another.<\/p>\n

Sometimes people will use logical structures in everyday speech without even noticing it. You\u2019ll hear someone in a caf\u00e9 say, \u201cIf it\u2019s raining, I\u2019ll bring my umbrella. It\u2019s raining\u2014so, obviously, I brought my umbrella.\u201d Pretty basic stuff, but that\u2019s the same pattern as what\u2019s in the textbooks. It\u2019s funny how these rules sneak into casual conversation, hiding in plain sight while everyone\u2019s focused on what coffee to order. Even outside formal philosophy or mathematics, our brains naturally turn to these patterns all the time\u2014sometimes, just to prove a point in an argument about nothing.<\/p>\n

Deductive Soundness<\/strong><\/p>\n

There\u2019s one catch, though. A deductively valid argument is not necessarily true. By definition, validity simply means that, if an argument is constructed without false premises, it will always yield a true conclusion. That \u201cif\u201d in there is key.<\/p>\n

It might seem like a trivial difference, but distinguishing between validity and soundness actually trips up a lot of people\u2014including, if I\u2019m honest, folks who should know better. It\u2019s not uncommon to see a perfectly valid argument get mistaken for proof of something in the wild, especially online. Scroll through any comment section in 2025 and you\u2019ll spot examples faster than you can hit refresh. When you peek under the hood, though, the supposed \u201cproof\u201d collapses if just one premise doesn\u2019t hold up. In other words: a step-by-step argument can still take you nowhere if you started on the wrong foot.<\/p>\n

Take the above example. Just because the premises state that Max is the tallest of the three doesn\u2019t make it so. Perhaps I mistook Max for Bill. Perhaps there I had something vindictive in mind. Whatever the case may be, it\u2019s not important. What is important in assessing the validity of the argument is its structure, and, in this case, the structure is impeccable.<\/p>\n

When assessing the soundness of an argument, however, the truth does come into play. If it turns out that Max is not the tallest of the three, then the above example is what is known as an unsound argument. This is because the relations between the three people are not accurate. To once again refer to the stuffy language of the textbook:<\/p>\n

An argument is deductively sound<\/em> if and only if it is deductively valid and all its premises are true. An argument is deductively unsound<\/em> if and only if it is not deductively sound. (p. 12)<\/p>\n

The easiest way to remember the difference between deductive validity and soundness is to think of validity as the structure of the argument takes\u2014If A, then B; A; therefore, B. Soundness, on the other hand, is the substance of the argument. If one cannot present the former, then the latter won\u2019t be taken seriously.<\/p>\n

}}<\/p>\n","protected":false},"excerpt":{"rendered":"

The word logic is derived from the Greek word logos. Logos has several nuanced meanings, but the one with which I am presently concerned pertains to deductive argument. Logic is simply the rules by which one must abide in order to present a valid, deductive argument and nothing more. In the political environment in which we live, one […]<\/p>\n","protected":false},"author":1,"featured_media":114152,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[117],"class_list":["post-114151","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-marketing","tag-migrationwa"],"yoast_head":"\nLogical Validity v. 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