The Laws of Thought

Nothing continues to amaze me more than the breakdown the business world and perhaps in society of an understanding of basic logic. By basic logic, I mean what are known by Western philosophers from Aristotle, to Aquinas, to Ayn Rand as the Laws of Thought. The laws of thought are the fundamental rules of logic that prescribe how a rational mind must think. To violate any of these laws is to be irrational. For the record, they are:

  1. The Law of Identity
  2. The Law of Non-contradiction
  3. The Law of the Excluded Middle

Let’s take a brief look at each.

Law of identity. Sometimes referred to as the existence principle, this law simply states that everything that is exists. The thing is the thing. A is A. A table is table. We can agree to call the table a chair but that does not change the fact that, in essence, it is still a table. Abraham Lincoln is attributed as posing the following question, “If you call a dog’s tail a leg, how many legs does the dog have?” His answer was, “Four, legs are legs, not tails.” This law sounds almost absurd, but when combined with the next two laws it makes for a powerful system.

Law of non-contradiction. Also, known to strict logicians as the Law of Contradiction, this law is really the fundamental principle of all thought. The law states that nothing can simultaneously be and not be. It is this law that I see broken most often especially during project management meetings. Customers will ask for, and stupid professionals will allow, contradictory requests. “We need these additional tasks complete, but don’t go over budget.” Or, “We don’t have time to test the system, but we want complain about it if it fails.” Commonly, we also see this at work in people who are against certain aspects of value pricing. For example, Ron posted reply from Tom Kane earlier this week. Kane’s first paragraph read in part, “I didn’t say timesheets are needed to track costs.” Followed by, “The reason to track hours on a fixed fee matter is so you can determine whether a law firm is recovering its costs and making a profit.” This is clear violation of this law. Tom is being irrational, as are most opponents of trashing the timesheet.

Law of the excluded middle. This is the most difficult to understand, it states that each and every thing either is or is not. The best example is this example: I am either alive or I am dead, but I cannot be alive and dead. Morbid, I know, but it makes the point clear. The famous example of an attempt to falsify this law is the statement, “This sentence is false.” Many people are caught on this because it appears to violate this law, but it does not because it is a contradiction and therefore already irrational.

Many people challenge these laws under Karl Popper’s falsification principle, since these laws cannot be falsified, but then again, neither can Popper’s falsification principle. Until otherwise noted, I will be using these laws. This sentence is true.


  1. Very interesting Ed. I am much clearer on this now. This sentence is false (maybe).



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