I have always been intrigued by the metaphors of Scripture. And there are a lot of them. There is no other way to speak of life in a totally distinct realm other than to use terms that are meaningful in ours? In chapter one Peter has talked about entering a spiritual realm by a “new birth” (a this-world occurrence, 1:3), having an “inheritance” in heaven (a normal social custom, 1:4), and being “redeemed” by a death (as in a slave market, 1:18). And now in 2:1 he talks about “thirsting” like newborn babies for the milk of God’s Word. Let's examine this last metaphor. What is it that Peter want us to picture in our mind when he speaks of "thirsting" for spiritual milk?
It is obvious that as believers we desperately need nourishment to grow and maintain a robust health. Without the regular provision of the mother, the baby will die. Would this happen in the spiritual word being described by this metaphor? At this point we must be careful not to build our theology solely on metaphors. It is clear that if, in this life, we quit eating we will die. Whether or not it would be true in the world of the Spirit depends on the more extensive theological teaching of scripture and theology.
The metaphor suggests that the milk that nourishes our theological life is to be both pure and spiritual. While the Greek logikos can mean “rational,” here its connection with the “word (logos) of God” in 1:23 makes it refer to Scripture. It is God’s word that nourishes the child of God. It is natural for us to “cry out for this nourishment” (NLT), especially now that we have tasted it and found in it the kindness of the Lord. (v. 2)
One caution. Although we ought to desire the spiritual milk like newborn babies, the metaphor does not encourage us to remain that way indefinitely but to grow up into the fullness of all that salvation means.