When the Reformed theology describes the universal offer of salvation as sincere, it does not merely mean that the human preacher, who obviously cannot distinguish with certainty between the elect and the non-elect, must for that reason issue to all men indiscriminately a most sincere offer of eternal life and an equally sincere invitation to accept that offer. It most assuredly means that, but it means incomparably more. The Reformed theology insists that God Himself, who has determined from eternity who are to be saved and who are not, and therefore distinguishes infallibly between the elect whom He designed to save by the death of Christ and the reprobate whom He did not design to save, makes on the ground of the universally suitable and sufficient atonement a most sincere, bona fide, offer of eternal life, not only to the elect but to all men, urgently invites them to life everlasting, and expresses the ardent desire that every person to whom this offer and this invitation come accept the offer and comply with the invitation.R. B. Kuiper, For Whom Did Christ Die? (Eugene, OR: Wipf and Stock Publishers, 2003), 86.
Observe what Kuiper says about the gospel in the above quote. It is:
1) An "Offer" and an "Invitation."
2) That it is "God Himself" who is offering Christ to all that receive the external call, and not merely us who are ignorant of the special decrees/"designs" of God.
3) That the offer by God is "most sincere, bona fide," or well-meant.
4) That this sincere offer is based or grounded upon a "universally suitable and sufficient atonement" by Christ.
5) That God "ardently desires" compliance from all that hear the call, and "gives expression" to this ardent desire in such a way that he "urgently invites" all. In other words, the revealed will of God is an active principle (he "expresses" it by urgent invitations) in God to the effect that he ardently desires gospel compliance from all unbelievers, whether elect or not.
R. B. Kuiper (1886–1966) was President of Calvin College (1930–33) and Professor of Practical Theology at Westminster Theological Seminary (1933–1952). He finished his career as President of Calvin Seminary.