The author's purpose for writing is not at first apparent. Some have suggested it was written as an antiexclusivistic tract, demonstrating that even a Moabite woman could become attached to God's people. Others feel the author was simply accounting for the ancestry of King David. But the recurring emphasis is Yahweh's unobtrusive activity in the lives of devout but otherwise ordinary individuals. Through their faithfulness and humble loyalty, he gradually accomplishes his purpose. In this way Ruth illustrates biblical and theological synergism. Far from canceling human-kind's free will, God's sovereignty is demonstrated and accomplished through the willful faithfulness of his servants.
In some ways the title of the book is misleading. Ruth is one of three main characters, and she takes the initiative in the events of ch. 2. But in ch. 3, it is Naomi who takes initiative; in ch. 4, Boaz. One could easily argue that the book centers around Naomi rather than Ruth, since Naomi eloquently states the problem to be addressed (1:20-21) and overshadows her daughter-in-law at the book's climax (4:14-17). But in another sense, neither of them is the central character. “The implication throughout is that God is watching over His people, and that He brings to pass what is good. The book is a book about God” (Cundall and Morris, 242).
Other theological themes in Ruth are derived from this emphasis on God's sovereignty. For those who are committed to his service, there are no mundane or commonplace occurrences. For the Christian, the distinction between sacred and secular is unnecessary, for all of life is sacred. This is beautifully illustrated in the surprise ending of Ruth (4:17), where we learn that these very ordinary folk became the ancestors of Israel's greatest king and, indeed, of the future Messiah.
Finally, some have overemphasized the theological significance of the kinsman-redeemer (gō'ēl) in Ruth. It is true that this little book provides valuable insight into the meaning of redemption (see commentaries). But the parallel should not be pressed since Ruth had a legal claim on her kinsman-redeemer, whereas the people of God have no such claim. We rely solely on the mercy of our Redeemer. A more pertinent lesson from the book is the emphasis on family values. Throughout this charming story, the characters are conscious of family ties and their responsibilities. This was, in fact, an integral element in their righteous conduct. This message is needed today.