Relations between the Persons of the Trinity

Unfortunately, much teaching on the doctrine of the Trinity focuses on how the one is three and the three are one, with little attention given to the actual relations among the divine Persons. In his introduction to the book Retrieving Eternal Generation, Trinitarian theologian Fred Sanders (co-editor of the book), notes that we must not lose sight of the important truth that....
...the Son is eternally begotten (or generated) from the Father. It is not enough to say that the Son is God; we must see that he is God the Son, not just God-in-general. Sonship, or eternal generation, is what gives both form and content to the relation between the Father and the Son: the relation has the form of fromness, and the content of filiality. Whenever the nature of that relation is left unspecified, any articulation of Trinitarian theology becomes brittle and disconnected.
Picture from the cover of "Retrieving Eternal Generation"
Without eternal generation, the constellation of truths that compose the doctrine of the Trinity remain just so many points of stellar light; they are stars that fail to constellate [see the illustration above]. They remain strangely isolated facts about threes and ones, essences and persons, in the cold vacuum of theologoumenal abstraction. 
In modern times, the doctrine of the Trinity is often taught in this disconfigured, unconstellated way: set forth as a teaching about one God in three persons as if that were the main business of the doctrine, with the possibility left open that the actual relations of the persons do not need to be specified, but could be as a matter of detail. But this rough-and-ready approach is clean contrary to the systematic needs of a coherent doctrine of the Trinity. It is not how the great, central tradition of Christian teaching has presented the doctrine. Nor is it how we first encounter the reality of the Trinity in Scripture. 
For a GCI-produced You're Included interview with Fred Sanders titled, "Adoption and Prayer in the Trinity," go to