When I was in college, I remember naively signing up for a course called “Introduction to Logic.”  

It turned out to be one of the greatest courses I have ever taken.     

Logic is the basis for philosophy, mathematics, and science. It helps you analyze arguments by stripping them of emotion and bias and looking solely to the reasoning behind them.

You can use this.

Rules of Inference

An argument is a series of statements, known as premises, that end with a conclusion. An argument is considered valid if it takes a form that makes it impossible for the premises to be true and the conclusion to be false. Practitioners use Rules of Inference to determine if the argument is valid. 

Most people recognize Rules of Inference, even if they don’t know the formal name. The most basic Rule is called Modus Ponens. It goes like this: “If P is true, then Q is true. P is true.  Therefore, Q is true.”   

In English: “If I am Chinese, then I am human. I am Chinese. Therefore, I am human.” 

You use Rules of Inference in almost every aspect of your life daily.   

Logical Fallacies

That brings us back to the starting point: the “premise.” A premise must be true if it is going to support an argument. A premise that is not true is called a logical fallacy. A logical fallacy leads to arguments that seem indisputable but prove nothing.  

When you look at it logically, you will be amazed how many of the arguments put forth by politicians, social media posts and your relatives are based on logical fallacies. Logical fallacies occur so often that they have been categorized by type. You can find them by a simple web search. Here are 5 of the most common.  

Ad Hominem

This fallacy attempts to defeat an argument by attacking the opposition’s intelligence, professional qualifications, morals, reputation, or personal character. “That so-called professor.” An Ad Hominem attack is intended to distract the viewer from a valid argument. 

Post Hoc, Ergo Propter Hoc

This assumes that if something occurred after an action, then it must have been caused by the action. “I ate a peach and then I got sick, so the peach must have made me sick.” The proponent ignores any other possible cause of the sickness. 


The proponent anticipates a weaker version of an opponent’s argument so it can be easily attacked. One person says, “I like sandwiches more than salad” and the other person replies “You must hate salad.” The proponent intentionally misconstrues the speaker’s statement.

Slippery Slope

The proponent claims, with insufficient evidence, that one action will prompt a chain reaction that ends with a dire consequence. Each link in the chain must be examined for truth.

Alternative Truth

Also called disinformation. The proponent simply denies facts to control the story. It is the hallmark of untrustworthy people.

On the topic of aging, logic can be a lifesaver when you are dealing with a family member who has begun the descent into dementia, mental illness, or substance abuse. These conditions often become evident only when the family member starts using logical fallacies to support an argument. If you can recognize illogical behavior, then you can start taking action to help the family member that much sooner.  

On the topic of everything else, logic can make you a smarter listener, a better debater, and a more informed voter. It would be well worth your time to do some research into logical reasoning.

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Virginia Hammerle is in her fourth decade of practicing law. She is Board Certified in Civil Trial by the Texas Board of Legal Specialization and an Accredited Estate Planner. Contact her at legaltalktexas@hammerle.com or visit www.hammerle.com. This column does not constitute legal advice.