The Scripture you say are a rule and a line: but are they not (as the Church of Rome imagineth) like a rule of lead, which may be bowed everyway at men’s pleasure.
“They are as a rule of steel, that is firm and changeth not. (Matt. 5:18; Psalm 19:9) For seeing they are sufficient to make us wise unto salvation, (as is before proved): it followeth of necessity, that there is a most certain rule of truth for instruction both of faith and works, to be learned out of them, by ordinary means of reading, prayer, study, the gifts of tongues, and other sciences, to which God promiseth and assistance of his grace (Job 5:39; James 1:5). And this sword of the Spirit, which is the word of God written, (as the example of Christ, our General Captain showeth, Matt. 4) is delivered unto us by the Holy Ghost, both to defend our faith, and to overcome all our spiritual enemies, which the Devil and his instruments, false Prophets, Heretics, Schismatics, and such like. (Eph. 6:17) Therefore the holy Scriptures are not a nose of wax, or a leaden rule, (as some Papists have blasphemed) that they may be so writhed every way by impudent Heretics, but that their folly and madness (as the Apostle saith, 2 Tim. 3:9) may be made manifest to all men.”
Ussher identifies two practical purposes for the Scripture being an unchanging standard – apologetic and polemic. Scripture is unchanging as the basis for Christian apologetic and as the grounds to “overcome all spiritual enemies” which he goes on to elucidate. Spiritual warfare the Scripture speaks of throughout its pages is a topic ignored by modern text critics and contemporary Evangelicalism. Muslim apologists identify an insurmountable weakness in the Christian Faith because of the low and changing view of Scripture brought on by modern text critical practices. Uncertainty has replaced divine faith, handicapping the Church and transforming the once bold assertion of “Thus saith the Lord,” into a pusillanimous whimpering of ambivalent concessions.
The Devil does have his instruments but the modern Evangelical acts as if the unchanging Scripture is unnecessary to defeat his schemes. Considering most modern English Bibles remove any reference to Lucifer in Isa. 14:12, in another generation, the fallen angel, Lucifer, may no longer be believed to exist. And if there is no Lucifer, who Satan is, if there is such a person or thing, becomes problematic. The most skillful of enemies are the ones who convince those they wish to defeat that they do not exist. See Daniel 8:25, “And through his policy also he shall cause craft to prosper in his hand; and he shall magnify himself in his heart, and by peace shall destroy many: he shall also stand up against the Prince of princes; but he shall be broken without hand.”
See Hava Lazarus-Yafeh, “Some Neglected Aspects of Medieval Muslim Polemics against Christianity,” Harvard Theological Review, 89:1 (1996), 61-64. The historical critical method has not only had negative impact on Christianity in the West but also on the world stage: “Muslim scholarly criticism of the Hebrew Bible and New Testament never brought about a corresponding study of the Qur’an. When European biblical criticism was brought to the Muslim East in the nineteenth century, it served only as an additional corroboration of the traditional polemical arguments about the falsification and unreliability of the Hebrew Bible and New Testament.”