This article addresses the issue of the relationship between God’s law and secular law, and presents a thesis for the legitimacy of the right to the objection of conscience “in which the voice of God speaks.” Considerations relate to conscience as the power of knowing good and duties, the universality of this knowledge, its legitimacy and conditions for its reliability. By referring to stoicism and neo-Platonism, but especially to the elements of St. Paul’s theology and the views of Benedict XVI, the author shows how important it is to introduce the category of nature and conscience to a secular, rationalist reflection on law. He presents the position of Christian theologians who spoke out against religious law and his own arguments, as well as the view expressed, among others, by Benedict XVI about the corrective role of religion with respect to human reason, as well as the importance of human reason for religion. The author also highlights the significant lack of reflection on natural law in modern science and the dramatic consequences thereof, such as the denial of the right to conscientious objection.