Structure of an Argument

You are probably already familiar with the word “argument” as its used quite often in casual conversation. In everyday parlance, argument means a spat or disagreement between two or more individuals over a particular topic. However, in the lingua franca of logic, the definition of an argument is further expanded to incorporate “a statement, reason, or fact for or against a point.” In other words, an argument is the reasoning constructed to support a position on x, y or z.


Now that we have properly defined an argument, let's move on to its structure within logic. An argument is composed of the following:

  1. Premise

  2. Turnstile

  3. Conclusion

That's it; just three parts compose the reasoning for every human's world view who has ever existed or will ever exist. Anything that falls outside of this particular structure is not considered an argument. It could be advice, a belief, an explanation, or other types of non-arguments, which are beyond the scope of this particular post.

The premise is a proposition which give reasons, grounds, or evidence for accepting the conclusion. The turnstile is a word or phrase such as thus, therefore, etc. that immediately precedes the conclusion. Last, the conclusion, is the proposition which is inferred from the premises. Note, some sources do not consider the turnstile to be a part of an argument and will just refer to the premise(s) and conclusion as the components of an argument.


Let's examine the following argument:

  • All mammals have hair.

  • Dogs have hair.

  • Therefore, dogs are mammals.

Here, the premises are the propositions “all mammals have fur” and “dogs have fur.” The turnstile is the word “therefore,” which is immediately followed by the conclusion “dogs are mammals.” That's it; a simple, instructive example of an argument, which happens to have a true conclusion. Let's try another:

  • It generally rains on Wednesdays in April.

  • It's April and tomorrow is Wednesday.

  • Therefore, it will rain.

In this example, the premises are “it generally rains on Wednesdays in April” and “it's April and tomorrow is Wednesday.” Following the turnstile “therefore,” the conclusion is “it will rain.” However, unlike our example before, the conclusion of this argument isn't necessarily true (i.e., there's a possibility that it could be wrong).

Let's try another argument that's more germane to pseudo-scientific arguments that are often encountered online:

  • My neighbor's child started to show signs of autism after having multiple vaccines around the age of one.

  • Thus, vaccines cause autism.

There is only one premise here which is the proposition “My neighbor's......age of one” and the conclusion is “vaccines cause autism.” Now, as we know due to the preponderance of scientific evidence showing no link between vaccines and autism, the conclusion is false. The error in this argument occurs in the premise. Specifically, a “false cause” logical fallacy (i.e., correlation doesn't mean causation) was committed, which renders the entire argument bad. Hence, the owner of the argument should replace it with a new argument; hopefully, one that doesn't contain a logical fallacy. If the new argument again contained a logical fallacy, it would have to be rejected once more. More on the formal definition of a logical fallacy as well as the various types later. 



At this point, you should be quite comfortable with the definition of an argument on your quest for critical thinking mastery. The premise, turnstile and the conclusion are the pieces that compose every argument that has ever been made or will ever be made. While the words that compose each piece may be different, the structure is always the same. Keep in mind that these arguments that we tell ourselves and those around us are what we use to shape our worldview. Therefore, it is paramount that these worldviews are built from a solid foundation of good arguments.