One decries circular reasoning with reasoning.  By what does he reason?  The laws of logic.  He assumes the laws of logic to argue his position.  How does one prove the laws of logic without logic? Hence, the one complaining of circular reasoning depends on circular reasoning for his argument against it.  One proves the laws of logic by using the laws of logic.

The accusation of circular reasoning proceeds from a false claim of neutrality from the accuser.  He assumes laws.  That isn’t neutral.  That starts with assumptions.  Everyone begins with assumptions. All reasoning arises from presuppositions.  The allegation of circular reason refutes itself, because it begins with laws no matter what the presupposition.

Everyone reasons from the uncaused cause, the prime mover, which is one.  Some reason from the only One, the actual Cause, the one and true God, and the others get the placebo.  Some regress to the Cause and others stop short not because of ignorance, but rebellion.  Every unbelieving person knows God and suppresses the truth in unrighteousness.  Like Jesus said, he hates the light because his deeds are evil.

Only God argues from neutrality, because only God is unaffected.  Everybody knows this.  They know it, but they don’t like to retain God in their knowledge, because they thanklessly reject the goodness of God and walk after their own lust.  God alone, with Whom is no variableness or shadow of turning, provides objective truth.  All the truth is His truth.  Because there is a God, truth is absolute.

The rebel sees truth as relative.  If truth is relative, then it isn’t one, and everyone can do what he wants.  At least in his deluded mind, he operates as a free agent outside of judgment.  In the real world, the only one, he’s going to pay the price for his sin.  This is something else everyone knows.  It’s why when you break the window of an unbeliever, he wants a new window and not rehabilitation.  It’s also why suicide and widespread manic entertainment everywhere that can desensitize the pain of conscience.

Everyone functions in circular reasoning, either starting with God or with something of his own choosing, either God or an idol from God’s creation — science, work, pleasure, government, money. Most stop short of a full regression to the first Cause, and choose their own along the way.  People either worship and serve the Creator or the creature, but everyone worships.  This is why you’ll notice religious fervor with agnostics and atheists.  God might be ejected from the public square, but religion never will.  Man either worships God, himself, or things.

A corollary of valid circular reasoning is arguing for the Bible from the Bible.  This is a primary point of Paul in 1 Corinthians 1-3.  God doesn’t turn to His creation to prove His Word.  It is spiritually discerned.  God Himself testifies of its truthfulness in men’s hearts.

Sure, the Bible can be proven in other ways besides circular reasoning, but circular reasoning is the best argument, because God Himself is its best witness.  And since the problem isn’t knowledge, but rebellion, a person’s nature must be affected by the supernatural to believe it.  Someone doesn’t believe because he is given a better argument, but because He has been persuaded internally by God Himself, the Holy Spirit.  If it was only an intellectual problem, other arguments might be better, but since it is a volitional one, only spiritual weaponry will do.  God is glorified in this methodology, something that really irks unbelievers, since their view of the world revolves around themselves.

So, circular reasoning is a valid argument as long as the premises are true.  Irony alert.  Everyone argues from circular reasoning.  Christians argue with validity.  Everyone else argues fallaciously.  A second irony alert.  Unbelievers assume that all circular reasoning is wrong.  They use circular reasoning to do so.