The Three Acts of the Mind

Unfortunately, this simple explanation of logic is not found on the web--at least not easily available. Of course this is not my original thinking on the subject, but something which Peter Kreeft presents in his book, Socratic Logic. This brief introduction has been one of the most helpful tools for my writing and thinking.

The 1st Act of of the Mind deals with definitions; words or terms must be clarified. The 2nd Act of the Mind focuses on propositions, or statements; the sentence is either true or false. The 3rd Act of the Mind is concerned with line of argumentation, e.g., the form of Modus Ponens--If A, then B. A, therefore, B.

Kreeft indicates that these are the three ways to reject or accept an argument. In the case of rejecting an argument, a term is ambiguous, a premise is false, or the form of argumentation does not guarantee the conclusion follows from the premise.

I think a short example should help explain this more clearly, if not, I suggest looking on page 33 of Kreeft's book, which includes a handy chart. If it is raining in Chicago, then it is raining in Illinois. It is raining in Chicago. Therefore, it is raining in Illinois. Beginning with the 1st Act of the Mind, it is helpful to define what you mean by the terms Chicago and Illinois. Chicago is usually assumed to be the midwestern city, the "Stacker of Wheat" as Carl Sandburg would say. Perhaps the most robust definition would indicate the degrees of longitude or latitude. But by doing this clarifying, a person avoids the objection of other towns named Chicago that exist in other states, or other places that use the name Chicago.

The next step is to look at the statements. If we understand Chicago as we defined it, and Illinois as the common understanding of the state in the midwest United States of America, it seems that we can accept that it is true "If it is raining in Chicago, then it is raining in Illinois." The second premise, "It is raining in Chicago" is either true or false, but has to be true in order for the conclusion to be true. A person would ask for evidence that it is raining in Chicago to agree with the premise.

The 3rd Act of Mind, concerned with the form of argument. In this case, the basic valid form of Modus Ponens is used, so the argument is valid.

Will Durant may be wrong in saying that "nothing is so dull as logic," but he is correct by adding that "nothing is so important" as logic.

Read articles and listen to audio by Peter Kreeft at http://www.peterkreeft.com/home.htm