John Calvin's proof for existence of Satan
In the Institutes of the Christian Religion I.14.17, John Calvin argues that the devil (or satan) and demons must exist in the world, because there must exist an agent that mediates between the goodness of god and the evil happenings in the world, such that this or these agents do evil, but they remain under god's commend so that god may utilize their evil for ultimate good. Calvin argues from the prologue of Job, that the satan wishes to afflict Job to his harm and expose his bad character, but god commands satan to afflict Job to prove his faithfulness. If good were to afflict Job directly, then it would be very difficult to demonstrate how god is entirely good. Calvin provides other examples as well that are similar to satan in Job and many biblical proof texts to support his argument.
In the Institutes I.14.17-18, Calvin also argues that the devil (or satan) must be servant of God, because there is only one god. Calvin argues against dualism's idea of two gods (one good and one bad), because there is one and only one god. God could not truly be sovereign if there was an equal and opposite bad god out of his control. Calvin argues that this explains the many biblical verses that indicates Christians will be tempted and afflicted to a limit, because the devil and demons may only go so far as god allows.
Calvin concludes that the devil must exist as god's servant to explain evil, but also to explain the assurance that evil will ultimately be overcome. Unless the devil and demons were under god's control, there would be no guarantee that they would be defeated in the end, as many scriptures indicates.
Friedrich Schleiermacher's rebuttal
Friedrich Schleiermacher argues that Calvin's proof texts are not "referring to the devil", and any references to the devil by Jesus and his contemporaries are not derived from divine revelation, including the Old Testament. Schleiermacher is right because there are only a handful of verses in the Old Testament that arguably reference demons (i.e. satyr in Isa 13:14; or shade in Deu 32:17; Psa 106:37, etc.) and this is in stark contrast to the frequent reference to demons in the New Testament (especially in the synoptics). Additionally, the modern idea of the devil (or satan) in the old testament is a conflation of many independent stories throughout the bible, and it is hasty generalization to identify the serpent in the garden of Eden with the satan in Job, or with lucifer in Isaiah, with the evil spirit that tested Saul or Ahab, and so on.
Schleiermacher also argues that devil and demons were an artifact of the first century cosmology, and were used to explain phenomena in an way that is obsolete today. (Karl Barth is in agreement when he said that believing in demons makes us a little demonic and he argued that Christians should disbelieve in demons too.) Schleiermacher also explains that modern Christian theology no longer has any need for the devil or demons in order to affirm or deny its dogma. He explains that the devil or demons originated in oriental dualism, and that the Jewish people was modified this dualism between a good and evil spirits (god vs devil or angels vs demons) to allow people or spirits to be servants of God that were not impeccable. Schleiermacher praises Calvin's attempt for assimilation, but also chides him for retaining belief in a devil and demons from an obsolete cosmology.
Conclusion
In conclusion, Karl Barth's demonology in his Church Dogmatics III/3 §50-51 is a helpful mediation between John Calvin and Friedrich Schleiermacher, because both Calvin and Schleiermacher provide strong arguments for-and-against the existence of the devil (or satan) and demons. I've included large citations from both Calvin's Institutes of the Christian Religion I.14.17-18 and Schleiermacher's Christian Faith 1.45.2 for reference.
"But even if we could regard some or, indeed all of the above quoted passages of Scripture as referring to the devil, there is still no reason for our accepting this notion as a permanent element in Christian doctrine and defining it accordingly so accurately that everything attributed to the devil could be conceived as a consistent whole. For Christ and His disciples did not hold this idea as one derived from the sacred writings of the Old Testament, or in any way acquired through Divine revelation; it was drawn from the common life of the period just as it is still present more or less in all our minds in spite of our utter ignorance as to the existence of such a being.
Since that from which we are to be redeemed remains the same (as does also the manner of our redemption) whether there be a devil or no, the question as to his existence is not one for Christian Theology but for Cosmology, in the widest sense of that word. It is exactly similar to questions as to the nature of the firmament and the heavenly bodies. In Christian Dogmatics we have nothing either to affirm or deny on such subjects; and similarly we are just as little concerned to dispute the concept of the devil as to establish it.
The Biblical usage merely shows that among the Jewish people the idea was really a fusion of two or three quite different elements. The first element is that of the servant of God who, while searching out the evil, has his rank and function among the other angels and cannot be regarded as expelled from the presence of God. Another element is that of the original source of evil in Oriental dualism, the conception being modified in such a way that the Jews alone were able to assimilate it. Now this function to some extent suggests joy in evil, and thus easily enough through some such fictitious story as the apostasy, the former could become the latter, or rather the name of the former pass over to the latter. It was obviously from these two elements that the acute mind of Calvin composed his formulas, though they will not harmonize in one consistent view.
[Institutes i.14,17 : Quamvis voluntate et conatu semper Deo aversetur tamen nisi annuente et volente Deo nihil facere potest.--Legimus illum se sistere coram Deo nec pergere audere ad facinus, nisi impetrata facultate ... 18, Deus illi fideles cruciandos tradit, impios gubernandos. (Institutes i.14, 17: 'Though averse to will and endeavor always to God, and, God willing, however, making a sign to nothing unless it can do. - We have read that Satan appears before God, nor dare to go for the deed, without obtaining the ability to ... 18, God is faithful to her tormented delivers wicked government.)]" [1]
17. The devil stands under God's power
As for the discord and strife that we say exists between Satan and God, we ought to accept as a fixed certainty the fact that he can do nothing unless God wills and assents to it. For we read in the history of Job that he presented himself before God to receive his commands [Job 1:6; 2:1], and did not dare undertake any evil act without first having obtained permission [Job 1:12; 2:6]. Thus, also, when Ahab was to be deceived, Satan took upon himself to become a spirit of falsehood in the mouths of all the prophets; and commissioned by God, he carried out his task [1 Kings 22:20-22]. For this reason, too, the spirit of the Lord that troubled Saul is called "evil" because the sins of the impious king were punished by it as by a lash [1 Sam 16:14; 18:10]. And elsewhere it is written that the plagues were inflicted upon the Egyptians by God "through evil angels" [Ps 78:49]. According to these particular examples Paul generally testifies that the blinding of unbelievers is God's work [2 Thess 2:11], although he had before called it the activity of Satan [2 Thess 2:9; cf. 2 Cor 4:4; Eph 2:2]. Therefore Satan is clearly under God's power, a n d is so ruled by his bidding as to be compelled to render him service. Indeed, when we say that Satan resists God , and that Satan's works disagree with God's works, we at the same time assert that this resistance and this opposition are dependent upon God's sufferance. I am not now speaking of Satan's will, nor even of his effort, but only of his effect. For inasmuch as the devil is by nature wicked, he is not at all inclined to obedience to the divine will, but utterly intent upon contumacy and rebellion. From himself and his own wickedness, therefore, arises his passionate and deliberate opposition to God. B y this wickedness he is urged onto attempt courses of action which he believes to be most hostile to God. But because with the bridle of his power God holds him bound and restrained, he carries out only those things which have been divinely permitted to him ;and so he obeys his Creator, whether he will or not, because he is compelled to yield him service wherever God impels him.
18. Assurance of victory!
Now, because God bends the unclean spirits hither and thither at will, he so governs their activity that they exercise believers in combat, ambush them, invade their peace, beset them in combat, and also often weary them, rout them, terrify them, and sometimes wound them; yet they never vanquish or crush them. B u t the wicked they subdue and drag away; they exercise power over their minds and bodies, and misuse them as if they were slaves for every shameful act. As far as believers are concerned, because they are disquieted by enemies of this sort, they heed these exhortations: "Give no place to the devil" [Eph 4:27, Vg.]. "The devil your enemy goes about as a roaring lion, seeking someone to devour; resist him, be firm in your faith" [1 Peter 5:8-9 p.], and the like. Paul admits that he was not free from this sort of strife when he writes that, as a remedy to tame his pride, he was given an angel of Satan to humble him [2 Cor. 12:7]. Therefore his exercise is common to all the children of God. But because that promise to crush Satan's head [Gen. 3:15] pertains to Christ and all his members in common, I deny that believers can ever be conquered or overwhelmed by him. Often, indeed, are they distressed, but not so deprived of life as not to recover; they fall under violent blows, but afterward they are raised up; they are wounded, but not fatally; in short, they so toil throughout life that at the last they obtain the victory.
Yet I do not confine this to individual acts. For we know that by God's just vengeance David was for a time given over to Satan, that at his prompting he should take a census of the people [2 Sam 24:1]. And Paul does not abandon hope of pardon as impossible, even if men are ensnared in the devil's net [2 Tim 2:25-26]. In another passage Paul shows that the promise mentioned above begins to have effect in this life, wherein we must struggle; and that after the struggle it is fulfilled. As he puts it, "The God of peace will soon crush Satan under your feet." [Rom 16:20.] In our Head, indeed, this victory always fully existed, for the prince of the world had nothing in him [John 14:30]. Moreover, it now appears in part in us, who are his members; it will be completed when we shall have put off our flesh, in respect to which we are as yet subject to infirmity, and will be filled with the power of the Holy Spirit.
To the extent that Christ's Kingdom is upbuilt, Satan with his power falls; as the Lord himself says, "I saw Satan fall like lightning from heaven" [Luke 10:18]. For, by this answer he confirms what the apostles had related concerning the power of their preaching. Likewise: "When a prince occupies his own palace, all his possessions are undisturbed. But when one stronger than he overcomes him, he is cast out," etc. [Luke 11:21—22 p.]. And Christ, by dying, conquered Satan, who had "the power of death" [Heb 2:14], and triumphed over all his forces, to the end that they might not harm the church. Otherwise, at every moment they would do away with it a hundred times over. For, such is our weakness and such is the power of his fury, how could we stand even in the slightest against his manifold and continuous attacks, unless we relied upon the victory of our leader? "Therefore God does not allow Satan to rule over the souls of believers, but gives over only the impious and unbelievers, whom he deigns not to regard as members of his own flock, to be governed by him. For the devil is said to occupy this world unchallenged until he is cast out by Christ [cf. Luke 11:21]. Likewise, he is said to blind all those who do not believe in the gospel [2 Cor 4:4]. Again, to carry out his "work in the sons of disobedience" [Eph 2:2], and rightly, for all the impious are vessels of wrath. Hence, to whom would they be subjected but to the minister of divine vengeance? Finally, they are said to be of their father the devil [John 8:44]; for, as believers are recognized as the children of God because they bear his image, so are those rightly recognized to be the children of Satan from his image, into which they have degenerated [1 John 3:8-10]. [2]
Sources:
1. Friedrich Schleiermacher, Christian Faith: A New Translation and Critical Edition, trans. T. N. Tice, C. L. Kelsey, E. Lawler. ed. C. L. Kelsey, T. N. Tice, (Westminster John Knox Press, Louisville: 2016). Section 163. pp. 997-998 [Christian Faith, 1.45.2; References were reformatted and paragraph breaks were added for readability]
2. John Calvin, Institutes of the Christian Religion. Ed. John T. McNeill. Trans. Ford Lewis. Battles. Philadelphia, PA: Westminster, 1960. pp. 175-8. Print. [Institutes 1.14.17-18; References were reformatted and paragraph breaks were added for readability]
Related: Calvin, CD III/3, christian faith, Church Dogmatics, demon, Demonology, Demons, Devil, Friedrich Schleiermacher, institutes of the christian religion, Job, John Calvin, Karl Barth, Satan, Schleiermacher
March 22nd, 2019 - 17:47
I much prefer Brunner on the topic: see Dogmatics, vol. 2: The Christian Doctrine of Creation and Redemption; Chapter 5: Angels, Spirits and the Devil. His conclusion is that although the Bible lacks sufficient references to form a coherent ‘Satanology,’ nonetheless “the Christian Faith is bound to admit the existence of a sinful supernatural power, and indeed of a purely spiritual sinful being, to which we can ascribe what we may call “Satanic” sin, in contrast to human sin.”