Covenant Theology is the apex of calvinistic theology. You cannot have a view of Calvinism that excludes a covenantal understanding of redemptive history. But what is a covenant? The most helpful definition of covenant theology comes from the uniqueness of Trinitarian relationship. Van Til himself acknowledged this relationship when he wrote:

The three persons of the Trinity have exhaustively personal relationship with one another. And the idea of exhaustive personal relationship is the idea of the covenant.

Hence, a covenant is a relationship; man cannot escape his covenantal existence. God has structured human history on the basis of His own intra-trinitarian relationship.

 Karlberg, p. 105. Quotation come from an article by Van Til on “Covenant Theology” in The New Twentieth Century Schaff-Herzog Encyclopedia of Religious Knowledge. 

 Thanks to Ralph Smith for his excellent insights (click on link to access document, which is IMPORTANT!).