A. believer said:
If they refuse to submit to the Word of God, then, indeed, they have no faith, but one can use a presuppositional apologetic to prove through, as Greg Bahnsen calls it, "the impossibility of the contrary," that whatever worldview they hold to, contrary to the Biblical one, is not rationally justifiable. The worldview that recognizes the triune God as the foundation of all reality is the only one that can consistently and rationally account for any knowledge at all. Apart from the Holy Spirit, people will still reject God even when this is demonstrated, but they can't reject God and make any reasonable claim to rationality at the same time.
God bless!