Book III: Of a Christian Common-wealth
In the previous two books, Hobbes has examined the "natural word of God," or the facts of nature that can be known by natural reason and has extended this natural order into a form of government based upon the laws of nature. Now, Hobbes considers the "prophetical word of God," or the elements of Christian faith that cannot be known by reason alone and yet must be obeyed. In Hobbes's discussion of the Leviathan, he insisted that all knowledge, belief, and power must stem from the sovereign in order to ensure peace. But in the case in which the sovereign's laws are contradictory to God's prophetical laws (they cannot be contradictory to God's natural laws, because they derive from them), a subject must know which laws to follow. Contradictory laws cannot both be followed, and having two masters, Hobbes writes, "makes men see double" (Chapter 39). Hobbes seeks to secure the sovereign's laws, which he has argued must always be obeyed, against possible conflicts with Christian religion. Hobbes's method in the final two books of Leviathan focuses less on his previous geometrical derivations than on that of radical exegesis--skillful readings and interpretations of Biblical scripture intended to show that Christian belief accords perfectly with his philosophical program. In the process, Hobbes undermines virtually all of seventeenth-century Christian dogma.
The belief that the world is the "kingdom of God" has, according to Hobbes, been responsible for the "...double [vision]" of Christian subjects, because to believe that both God and the civil sovereign are kings of the world causes divided loyalties. Hobbes demonstrates though his reading of scripture that the kingdom of God is not present until the world ends, and thus only the civil sovereign is king in this world.
Ecclesiastical authority established under the belief of God's constant presence in the world has deepened the problem of seeing double. The institution of Churches, popes, priests, pastors, and theologians--who possess power and knowledge that is supposedly founded upon authority outside of the sovereign's domain (i.e. the authority of God and revealed religion)--creates a chasm in the power structure of the Leviathan. A subject's knowledge and obedience is split between two heads of the commonwealth, and this will lead, as Hobbes has repeatedly argued, to civil war. As such a situation is against the laws of nature--in that it puts safety in danger--it is against the word of God for religious authority and civil authority to be split into two bodies. Thus the sovereign must also be the head of all religion.
Certain religious tenets, which seem to contradict the conclusions of Hobbes's philosophy, are also responsible for seeing double. Belief in angels, spirits, and miracles reinforces a belief in the immediate presence of the kingdom of God, which undermines the sovereign kingdom here on earth; thus Hobbes must show that such beliefs do not depend upon dogmatic faith. Ecclesiastical authorities have perpetuated these beliefs in people in order to keep their own power distinct from the sovereign. But all these beliefs are explainable by Hobbesian philosophy.
Because the universe is a plenum, incorporeal spirits and angels are impossible. When everything is made up of bodies, the concept of bodilessness is illogical. The experience of these phenomena is caused by the effects of the motion of matter upon the human brain, which make a person believe that he or she is seeing something that is really not there. Thus spirits, angels, and visions of saints are "idols of the brain," and to worship such idols is contrary to Christianity, diminishing one's faith in God, who is not present in idols. When such an idol of the brain is sent by God to deliver a message (i.e., by initiating a certain sequence of motions that reach the brain), then this idol is properly called an angel, but must be recognized for what it is, rather than worshipped or feared as an incorporeal entity.