Hailed by D.G. Hart as the "most important conservative Protestant thinker of the first half of the twentieth century and a guiding light for the first generation of Orthodox Presbyterians," J. Gresham Machen remains a staunch champion of the validity of the Bible. In John Piper's presentation to the Bethlehem Conference for Pastors (1993), the fellow Presbyterian pastor illustrates through J. Gresham Machen’s Response to Modernism how the defender of orthodox Christianity titled his work precisely so, declaring that "liberalism is vying with Christianity as a separate religion." An American Presbyterian theologian and professor of the New Testament at Princeton Seminary, Gresham wrote Christianity and Liberalism written as a response to modernist theology. Published in 1923, the work of Gresham presents how there are varieties of modern Christianity deriving from a historical basis and how a modern offshoot departs from traditional theology and doctrine. Machen details the erroneous progressive synthesis of God as the “father of all,” the rise of pantheism that has replaced orthodox Christian theology in modern churches, as well as the detrimental form of sermons preached without intending to convict sin or express the personal yet distinct relationship between God and man.
Machen specifies how Liberalism inherently separates itself from the root of the historical Church, specifically in how modernists view the nature and relationship of God and man. Piper continues to explain how Machen viewed the negative aspects of modernism being surmised of general traits: a suspicion of the past that is natural in view of the stunning advances of recent decades (science and technological progress), skepticism about truth and a replacement of the true with the category of useful (pragmatism, utilitarianism), and the denial of the supernatural.” As indicated by Machen’s writing, the modernists reinterpret the Bible without necessarily throwing out Christianity; instead manipulating the meanings and reinventing new creeds, symbols and messages to suit their ever changing agenda. Piper further articulates how progressive forms of Christianity differ from orthodoxy; stating that creeds and foundational principles are seen as relative - "if they are useful for one generation, good; if not for another, then they may be exchanged." However, Machen clearly affirms in Christianity and Liberalism that the doctrine of God’s eternal and unchanging nature serve as a presupposition from which the entire gospel clings. As modern liberalism does not acknowledge this aspect, the radical and pragmatic form of Christianity lacks in consistency and fails to encapsulate the physical, spiritual, and historical essence of the Judeo-Christian faith. Machen stresses that liberalism is opposed to God due to the progressive’s very interpretation of Him. He mentions how many churches have leaned towards saying that a conception of God is “unnecessary; [that] theology, or the knowledge of God is the death of religion; we should not seek to know God, but should merely feel His presence." However, emotions do not determine truth or the knowledge of what truth comprises of. Without knowledge of God, there is no basis for religion, Machen argues, as the knowledge of God is the very basis and foundation of the Christian faith. Furthermore, through his discussion analyzing non-theistic propositions, Machen clarifies plainly that the religion Jesus offered was triumphant only because of a “belief in the real existence of a personal God. And without that belief no type of religion can rightly appeal to Jesus today. Jesus was a theist, and rational theism is at the basis of Christianity.”
In light of liberal preachers teaching that God can only be interacted with through Jesus, Machen pours over the Sermon on the Mount, the account of the Prodigal Son, and reflects on the words of the psalmists to show that it is in fact insulting to Christ, not a form of allegiance, to suggest that God could only be made known through the figure of Christ. He intellectually utilizes prominent scriptural passages to expose how Jesus acknowledged that God revealed Himself through nature, through moral laws, and through the biblical text. By suggesting that man can only know God through Jesus dismisses all “real knowledge of God” and despises the intimate character of God expressed through the Old Testament and the revelation which Christ teaching’s brought which further assisted and made complete the testimony of Creator and His creation.
A unique critique Machen offers is commentary on the liberal focus on the “fatherhood of God.” He considers it strange how “modern liberalism is decrying theistic proofs, and taking refuge in a "practical" knowledge while the liberal preacher loves to use one designation of God which is nothing if not theistic; he loves to speak of God as "Father.” Most modern liberals, Machen asserts, do not either use the term literally or do so only when useful, not because of actual theological reasoning regarding God’s station to humanity. He links the usage of such a personal term to that found in other religions and where “father” is used to describe the transcended reality that is more akin to pantheistic or polytheistic inclinations. However, Machen claims that Jesus renewed the meaning of the term and identity of God as “something characteristically Christian” - being “father” to those alone who have been redeemed and have been exclusively made part of God’s family, thus legitimizing their title and position of being known as His children. Rejecting this notion, many liberals do not seem to value or cherish doctrinal creeds, the reality of sin, salvation, and the atonement, but instead are content with the idea of a supposed fatherhood for all humans due to a shared brotherhood. Machen rejects that, stating that the concept of a universal fatherhood is absent in both the Old and New Testament. He dispels the idea that the story of the Prodigal Son proves this bond, continuing to show how the parable displays God’s adoration for a redeemed sinner who has received salvation – Machen dissects the passage to the point of revealing that God does not share this bond with unrepentant sinners, as they are not His children - they are not apart of the family of God. Machen counters arguments of how God cares for all by expressing how God “cares even for those who are not His children but His enemies; so His children, Jesus' disciples, ought to imitate Him by loving even those who are not their brethren but their persecutors. The modern doctrine of the universal fatherhood of God is not to be found in the teaching of Jesus.”
Rejecting this form of doctrine and the demands of redemption, many turn to atheism, paganism, or substitute humanism for Christianity. It is arguable that the modern practice of Christianity is responsible in part due to the rise in atheism. Doctrine, church history, apologetic reasoning, intellectual Christian scholarship and achievement, and tradition are ignored, and are not adequately taught by a large majority of denominations. Followers of Christ profess their adoration for a merciful God while rebuking that mercy by consciously abandoning the standards which they claim to be so dear through lives that are conducted in quite a contrary manner. Machen notes how it is “useless for the preacher to breathe out fire and brimstone from the pulpit, if at the same time the occupants of the pews go on taking sin very lightly and being content with the standards of the world. Sin is not seen as sin or the weight of it is instead considered a flippant aspect and an unavoidable measure of being human. The “perfectionism” of the Second Great Awakening which spurred the motivation towards social reform earned Christians lauded praise by how they eliminated intolerable circumstances in the world through the efforts of abolition, suffrage, education, and temperance - rallying first and foremost for such change based on the principles of Christ and the inherent need of a sincere Christian to rise to the standards presented in the doctrine. Though perfection cannot be attained by mere mortals, the lack of attempt towards Christ’s perfection ought to be viewed as inexcusable by those who claim to follow Jesus who specifically calls and equips His "sons and daughters" to live up to such perfection. If sin is not realized, life is conducted in a fashion more like the humanist, pantheistic reasoning described by Machen. Instead, sin is excused on account of the fragility of human weakness and the presumed inability to change upon a conviction of the Holy Spirit to confess contritely, turn from moral failings, and live uprightly. Often, arguments of convivence overrule the high cost of Biblical morality.
Aligned with the severe demands of the Christian faith, Machen stresses in the conclusion of his chapter on “God and Man” how modern preachers attempt to win souls without “requiring them to relinquish their pride; they are trying to help men avoid the conviction of sin.” The preacher preaches about man’s goodness and how Christ’s message is good enough for them, rather than showing the inconsistency of that message with the entirety of Christianity’s foundational principles. Modernist Christianity appeals to modern culture instead of appealing to Scripture or Church history for authority. Out of desperation to be relevant to society, modernists Christians adapt their beliefs to fit the current era. A predominate vein of this progressive type of sermon and ministry lacks conviction and refuses to rage against the detrimental reality of human depravity as did ministers of old. Jonathan Edwards, George Whitefield, and fundamentalist preachers like Billy Graham, are spurned as being a source of condemnation instead of seen as ministers presenting the hope available purely due to Christ’s atonement. Ultimately, Machen specifies how such topics are not touched upon as such a mention would lower the pride of man. His work ensnares the folly of human reasoning, advocates how a liberal intellectual orientation skews the Gospel into a very different religion than genuine Christianity, and finally, illuminates how modern liberalism reassures the pride of man that such arrogance is justified.
 John Piper. " J. Gresham Machen’s Response to Modernism." Desiring God. 1993.
 J. Gresham Machen. Christianity and Liberalism. Grand Rapids, Michigan: W. B. Eerdmans Publishing Co, 55.
 Ibid, 55-57.
 Ibid, 58.
 Ibid, 59.
 Ibid, 60.
 Ibid, 67.
 Ibid, 68.