How then shall they call. ... - The apostle here adverts to an objection which might be urged to his argument. His doctrine was, that faith in Christ was essential to justification and salvation; and that this was needful for all; and that, without this, man must perish. The objection was, that they could not call on him in whom they had not believed; that they could not believe in him of whom they had not heard; and that this was arranged by God himself, so that a large part of the world was destitute of the gospel, and in fact did not believe; Romans 10:16-17. The objection had particular reference to the Jews; and the ground of injustice which a Jew would complain of, would be, that the plan made salvation dependent on faith, when a large part of the nation had not heard the gospel, and had had no opportunity to know it. This objection the apostle meets, so far as it was of importance to his argument, in Romans 10:18-21. The first part of the objection is, that they could “not call on him in whom they had not believed.” That is, how could they call on one in whose existence, ability, and willingness to help, they did not believe? The objection is, that in order to our calling on one for help, we must be satisfied that there is such a being, and that he is able to aid us. This remark is just, and every man feels it. But the point of the objection is, that “sufficient evidence of the divine mission and claims of Jesus Christ had not been given to authorize the doctrine that eternal salvation depended on belief in him, or that it would be right to suspend the eternal happiness of few and Gentile on this.”
How shall they believe in him ... - This position is equally undeniable, that people could not believe in a being of whom they had not heard. And the implied objection was, that people could not be expected to believe in one of whose existence they knew nothing, and, of course, that they could not be blamed for not doing it. It was not right, therefore, to make eternal life depend, both among Jews and Gentiles, on faith in Christ.
And how shall they hear ... - How can people hear, unless some one proclaim to them, or preach to them what is to be heard and believed? This is also true. The objection thence derived is, that it is not right to condemn people for not believing what has never been proclaimed to them; and, of course, that the doctrine that eternal life is suspended on faith cannot be just and right.