Intro to Logic: The Importance of Good Thinking

by Luke Muehlhauser on March 23, 2009 in Intro to Logic

Believing ourselves to be logical is common, but logic itself is rare.

Deborah Bennett

Good thinking can be hard work, and you have to practice it. But it can also be great fun, and spare you lots of pain and confusion from bad choices.

So, I’d like to introduce my basic course in logic. Not because I’m a paragon of logical thinking and need to educate everyone else, but because we all make logical mistakes – probably every day. Even some of the finest philosophers do. In truth, I’m doing this more for myself than for you. The best way to learn (or relearn) something is to teach it, continuously.

Probably, most of the people reading this blog have some familiarity with logic. But I think this will be a good review for all of us. And eventually, it will develop into a handy place to send other people who aren’t so logical. For example, there will be individual posts on each informal fallacy, why logic works, how to construct a valid argument, etc.

This first part of my basic course in logic is about the crucial importance of good thinking.

Who cares about logic?

People take many paths to truth. Most people use a combination of personal experience, gut feeling, and testimony from others to discern the truth. These methods might do you well enough to manage some relationships and get you to and from work, but they have a horrible track record when it comes to getting at truth about much of anything else.

The fact is that throughout history, nearly all the people who have ever lived have been wrong about damn near everything. Wrong about magic. Wrong about spirits. Wrong about gods. Wrong about medicine. Wrong about diet. Wrong about astronomy. Wrong about economics. Wrong about political theory. Wrong about chemistry and physics. Wrong about biology. Wrong about the afterlife. Wrong about the opposite sex. Wrong about psychology. Wrong about pretty much everything.

The reason is they were using the wrong tools. Your “feelings” are not designed to discern truth. That’s like trying to solve a math equation with your liver. It’s the wrong tool for the job.1

Likewise, personal experience is a terribly small sample from which to discern the truth. Several people can experience the same thing and walk away with wildly different impressions. Your personal experience has more to do with your history, your beliefs, your mood, your morals, and your perspectives than it has to do with the truth about “the world out there.”

Testimony from others is also problematic. First, because other people are usually as ignorant and biased as you are. It’s the blind leading the blind. For thousands of years humans have passed on wrong information to each other. Even the smartest human beings were wrong about damn near everything, as comedian Dave Barry wrote, “until about 1926.” The other problem is that everybody has an agenda. Somebody may be lying to you, or deceiving themselves and passing on bad information.

If you don’t care about truth, this isn’t a problem. If you care about truth and you’re using “gut feelings” to get at it, you’re almost certain to be misled, constantly. If you depend on personal experience or testimony from others, you won’t do much better.

So, we need some tools that are better designed to discover truth.

Here are some benefits of having good tools for discovering truth:

  • You can avoid scams, rip-offs, and con artists.
  • You can focus on what really matters.
  • You can engage with the real world, instead of living a confused fantasy.
  • As you understand how the world really works, you’ll know what you need to do to achieve your goals.
  • You can avoid really huge mistakes, like devoting your life or money or emotions to a false religion or a false ideology.
  • You can avoid making the world a worse place when you were trying to make it better. Think of religious crusaders or bloodletting doctors – they thought they were making the world better, but they actually made it worse, because they had bad ideas that came from poor thinking skills.
  • You can engage in humanity’s exciting quest to understand ourselves and the world we find ourselves in.
  • You can contribute to our common quest of finding and promoting solutions that actually work.
  • You can properly filter the masses of information that come your way in the information age.
  • You can improve your rhetorical and presentation skills, and your ability to persuade others.

Feelings, personal experience, and testimony from others – no matter how effective you feel them to be – are not good tools for the job. You need to build your truth filter with something better-designed for the task.

Logic is the right tool for the job. I’d like to show you why it’s the right tool for the job, and then teach you how to use it.2

I’d like to end with a quote from Lewis Carroll, who was best known for Alice’s Adventures in Wonderland but was most proud of his work on Symbolic Logic:

Master the machinery of [logic], and you have a mental occupation always at hand… that will be of real use to you in any subject you take up. It will give you clearness of thought – the ability to see your way through a puzzle – the habit of arranging your ideas in an orderly and get-at-able form – and, more valuable than all, the power to detect fallacies, and to tear to pieces the flimsy illogical arguments, which you will so continually encounter in books, in newspapers, in speeches, and even in sermons, and which so easily delude those who have never taken the trouble to master this fascinating Art. Try it. That is all I ask of you!

(Also see the post index to this Intro to Logic series.)

  1. Feelings are designed only for subjective truth: like love or art. If you “feel” in love, you are in love, by definition. But this only tells you what’s happening in your own experience, not what is really “out there in the world.” []
  2. Other methods, like science, are also useful, but they depend on logic, and are outside the scope of this post series. []

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{ 6 comments… read them below or add one }

Shane Steinhauser December 26, 2009 at 6:13 pm

Thank you for this series Luke. I’ve been meaning to learn logic for a while now, but bookstores and libraries don’t seem to carry books on logic. They always seem to have aristotle or kant but never a logic book.

You said that personal testamony and gut feelings are bad indicators of truth. That would seem to make the historicity of Jesus’ ressurrection (testamony), and the moral argument for God (gut feelings) illogical from the get go. Are personal testamony and gut feelings held to be bad by *all* logicians, or are those merely your personal ideas?


lukeprog December 26, 2009 at 9:22 pm


Whether or not gut feelings or testimony can serve as good evidence is a question for epistemologists, not logicians. But I don’t see any reason to trusthem, since they are wrong more often than they are right.


Leomar July 30, 2010 at 8:53 pm

Cognitive Behavioral Therapists also use a lot of logic and critical thinking tools, specially Socratic Questioning (you may want to post some post about it), to help people question the irrational beleifs that produce them anxiety, depresion and other negative emotions disorders and become more healthy human beings.

So I will made the emphasis on that, It’s really really helpful.

You may want to check:

In fact it’s because of these problems that a lot of the time they reject rationality in favor of religion or cults.

Great post.


roco September 18, 2010 at 8:21 pm

I like your theory of logic, i just didn’t like when you said that you do this for yourself just to relearn and not for the readers. thank you any way


lukeprog September 18, 2010 at 9:49 pm



Amie April 7, 2011 at 8:17 pm

I do not believe that any one that blogs on Atheism and common sense logic in the same place lacks extreme intelligence.


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