I often find it helpful to illustrate my point with extreme cases. Let's examine some well-known examples of unbelievers: Graham Oppy, a distinguished atheist philosopher specializing in philosophy of religion; Peter Atkins, an atheist scientist highly proficient in Chemistry; Stephen Hawking, a globally recognized atheist theoretical physicist and cosmologist; and Carl Sagan, a renowned astronomer and science communicator who identified as an agnostic.
For example, on the question of whether God exists, Carl Sagan once said:
An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed. (source)
Graham Oppy was asked the question of what it would take to convince him to believe in God during an interview on Premier Unbelievable?. He essentially expressed uncertainty, leaning towards skepticism that a new philosophical argument for God's existence would be persuasive to him, given the countless arguments for God he had already studied. Similarly, when Peter Atkins was asked on a different occasion, "Could anything convince you God exists?" he responded by stating that he couldn't think of any convincing factor, given his unwavering commitment to naturalism.
In light of individuals with such backgrounds—who genuinely grapple with the inability to conceive of anything convincing—I find it challenging to reconcile this reality with the notion that the gift of saving faith in Christ is universally accessible. It's difficult for me to envision someone like Graham Oppy simply "choosing" to embrace and exercise the gift of saving faith in Christ supposedly available to him, or simply "choosing" to become born again. Absent a miracle, direct revelation, or an encounter akin to Acts 9, I genuinely struggle to see how this could plausibly unfold.
If the offer of saving faith in Christ is a universal gift from God, does this extend to unbelievers like those mentioned earlier? If the opportunity for saving faith is accessible to all, can committed unbelievers such as Carl Sagan or Graham Oppy also avail themselves of this gift?