…the reality of the Christian life lived by the reality of the indwelling Spirit would suffer. As that reality was diluted evangelicalism kept up the appearances of true spirituality, the Christian life, by external means of organization and methods. It became more fashionable to talk and teach about Christian truth using the world’s categories as Christian truth began to be practiced according to naturalistic methods. In time this changed the ethos within evangelicalism even while the doctrinal statements remained the same. Quantitative replaced qualitative, image superseded substance, emotionalism supplanted theology, cultural relevance snubbed objective truth, while social action masqueraded as faithfulness to Christ.

Francis Schaeffer notes that by the latter half of the 20th naturalism had captivated much of the thinking in the west. In chapter five of True Spirituality he writes: “Our generation is overwhelmingly naturalistic. There is an almost complete commitment to the concept of the uniformity of natural causes in a closed system.” The basic assumption of naturalism is that all that exists is the material world, that everything can be explained by a series of biological, chemical causal chain. Unfortunately, this thinking began to seep into evangelicalism as well. Schaeffer writes: “Surely this is one of the greatest, and perhaps the greatest reason for a loss of reality: that while we say we believe one thing, we allow the spirit of naturalism of the age to creep into our thinking, unrecognized” (255).  When Schaeffer says “we”, he is speaking of evangelical Christians. He concludes that “little by little, many Christians in this generation find the reality slipping away. The reality tends to get covered by the barnacles of naturalistic thought” (263).

This explains why he thought naturalism was a real threat to the Christian way of life as it demeaned the unseen side of reality. One must understand that according to Christian teaching, reality consists of both the seen and the unseen (II Cor 4:18).  It is a fact that the actuality of the Incarnation brought these two inextricable aspects of reality into full view (Jn 1:18). However, as the American Enlightenment rolled into the 20th century, the champions of naturalism started to divide total reality (seen and unseen) into two separate parts where the unseen was separated from physical reality. Eventually, many, especially in the American secular academy and scientific community denied the unseen aspect of reality altogether.

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