Logic

What does the term 'circular' mean in the context that it is used here on this web site?

Comments

When philosophers call something "circular," they generally are making a logical characterization--it means that someone has somehow assumed the truth of what he or she is supposed to be proving, and thus "derives" the conclusion only by having the proposition expressed in the conclusion already present (and underived) within the premises of their argument.

An example might help. Suppose you asked me if there was any "proof" that God existed, and I produced the following argument:

(1) God says He exists.
(2) Because He is God, He would not lie.
(3) Hence, God exists.

I doubt that you would find this very compelling as a "proof," because both premisses (1) and (2) assume the existence of God, when that is the very thing I was supposed to prove to you. Here's the circle, briefly: How do I know that God exists? Because He said so. How do I know there is a God who could say such a thing? Because He exists. Feel like we're not getting anywhere here? It's because we're not--we're going in circles.

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