Berkouwer's basic criticism of Bultmann's concept of myth is that it is different from the New Testament conception of myth. He insists that, in the New Testament, "myth stands over against the truth (aletheia) of the history of Jesus Christ ... the decisive die has ... been already cast in the New Testament opposition to myth" (Holy Scripture, p. 254).
He rejects an existentialist conception of truth which is dissociated from the 'once for all' character of the gospel events (Holy Scripture, p.262) and which makes the modern world-view the norm by which the nature of the gospel is determined (Holy Scripture, p. 261).
Berkouwer holds that, in the New Testament, the concept of myth is not simply a harmless feature of a primitive world-view, requiring only to be reinterpreted for modern man.
He emphasizes that myth is that which "diminishes the truth of salvation" (Holy Scripture, p. 253).
Concerned with 'how (emphasis original) the Spirit wishes to guide us to salvation and joy through the real (emphasis mine) Scripture' (Holy Scripture, p. 263), Berkouwer refuses to set the existential (i. e. involving man in the entirety of his existence) work of the Sp[irit over against the real Scripture.
Thus, he avoids creating a 'mythical' Bible which is not the real one, but a projection of the existentialist (i. e. the hermeneutical principle used by Bultmann) imagination.
In the New Testament, myth is warned against because of its destructive influence, leading men away from the truth and the God of truth.