How can theology portray moral perfection as the work of God's grace while also upholding the genuinely human character of the transformation it involves? And how are we to view ordinary processes of formation, such as those we experience as children, in the context of a broader commitment to understanding sanctification as a gift? Prompted by such questions, this dissertation explores how natural processes of moral formation relate to divinely enabled moral change by placing a Reformed Protestant understanding of sanctification in conversation with recent social scientific research on early childhood development. In Chapter 1, I explore John Calvin's discussion of sanctification in the Institutes of the Christian Religion and the assumptions regarding sanctification which are at work in his pastoral practice. For Calvin our knowledge of God as our loving father establishes a relational context in which our moral agency is transformed. Unresolved tensions in Calvin's thought, however, leave open the possibility that subsequent accounts of sanctification will either completely divorce it from natural human formation or collapse the work of the Spirit into our understanding of natural formation. Chapter 2 on the Puritan theologian John Owen illustrates the former trajectory and Chapter 3 on the 19th century American theologian Horace Bushnell illustrates the latter. In Chapter 4, I introduce recent studies of child development, first presenting recent research on the cognitive, affective, and social capacities of infants and then looking at how moral agency emerges from these capacities in the context of a mutually responsive parent-child relationship. Here too, the relationship of love and commitment between parent and child provides the developmental context that enables genuine moral agency. In Chapter 5, I draw on the analogy of the parent-child relationship and the anthropological insight afforded by consideration of children to address the ongoing problems in the tradition and to argue that the process of sanctification is consistent with who we are as human beings while still dependent on our relationship to Christ in the Spirit.