A corollary theme to knowing God is the relationship between doctrine and devotion. While Packer holds it as true that the Christian understanding of salvation and ethics rests on the foundation of a relationship with God, this does not mean that doctrine is unimportant—in fact, much of the material in Knowing God is concerned with explaining proper doctrine. The first two parts of the book focus on doctrines relating to the nature and character of God, leading to the third part, which examines elements of Christian experience and devotion.

This approach stands in contrast to the way that some modern Christians—frequent targets of Packer’s critiques—exalt the element of devotion over doctrine, leaving traditional doctrines about God’s character by the wayside and asserting that what really matters is drawing near to God in one’s heart. Such Christians, Packer suggests, tend to downplay biblical portrayals of God’s wrath and jealousy or his role as judge, which Packer believes to be a fundamental error, noting: “The fact is that the subject of divine wrath has become taboo in modern society, and Christians by and large have accepted the taboo […]. We may well ask whether this is as it should be, for the Bible behaves very differently” (149). Packer argues that if one is only choosing to believe in those parts of the Bible’s depictions of God that they happen to like, then they are not really believing in God, but in a projection of their own sensibilities. Packer believes that this way of thinking will lead to a misunderstanding about the role of God as judge, together with his jealousy and wrath, as well as a misunderstanding of God’s love and grace.

Packer contends that one must wrestle honestly with what Scripture says about God to be led to true Christian devotion. In his view, a large part of the mistake made by those who reject the wrath and jealousy of God is that they have reacted against their own sense of what those words mean rather than delving deeply into the reasons why the Bible portrays God in this way. He notes that “Nobody would imagine a jealous God. But we are not making up an idea of God by drawing on our imagination; we are seeking instead to listen to the words of Holy Scripture […]” (167). Once one understands the biblical doctrines regarding the reality of evil and sin, Packer believes, such attributes as wrath and jealousy fall into place. For example, if evil exists in the world, then God cannot be ambivalent about it—to be morally perfect, God must judge evil. Through this lens, the Bible’s depiction of God’s wrath is simply the divine prerogative, exemplifying this virtue, put into action.

Packer argues that when such doctrines are rightly understood, then the doctrines of love and grace fall into place too—the remarkable extension of favor and mercy where none was warranted. Only in such a view, Packer believes, can one rightly understand both God and themselves, and be moved to proper devotion, awe, thanksgiving, and obedience in response to God’s freely-given, unmerited grace.