To bring anyone up to speed who may be rusty on their Protestant history, there are five solas that marked the Reformation. They are:
Sola Scripture - Scripture Alone
Solus Christus - Christ Alone
Sola Gratia - Grace Alone
Sola Fide - Faith Alone
Soli Deo Gloria - Glory of God Alone
Together they form a common confession: We are saved by grace alone, through faith alone, by Christ alone according to the Scriptures alone, to the glory of God alone.
All 5 Solas of the Protestant Reformation are intertwined. None of these doctrines stands alone as though it were in a vacuum. Each Sola both relies upon and informs the other 4 in order to establish a strong matrix of truth. Soli Deo Gloria in particular speaks to the big picture of all the other Solas, tying them together and answering the big “why?” questions of our lives.
Soli Deo Gloria and Sola Scriptura combined speak to why we believe what we do, or our epistemology. Soli Deo Gloria relies on Sola Scriptura for the authority of the doctrine itself. Indeed if it were not for Sola Scriptura, we would not know that all things were Soli Deo Gloria. It is from the Bible that this truth is explicitly revealed to us. Soli Deo Gloria informs Sola Scriptura by establishing the reason for which the Bible is our only infallible rule of faith and practice. If all things are for God’s glory, then we ought to honor and observe every Word that he speaks to us. In contrast, we ought not to ascribe that same honor and that same authority to those commands which do not proceed forth to us from God himself; thus establishing our principle of nothing more and nothing less than God’s Word.
Soli Deo Gloria and Solus Christus combined speak to why we are saved, or our soteriology. Soli Deo Gloria relies upon Solus Christus to establish the fact that Christ alone functions as our savior and that his sacrifice need not be supplemented. If there were another savior or the savior’s sacrifice needed supplements to be effectual, then those additions ought to be rendered some glory for their part in the process. This relationship also heavily implies the deity of Christ, as it can be deduced that the savior himself ought to be given glory for his sacrifice. Soli Deo Gloria informs Solus Christus by establishing the ultimate end for the atonement itself. God ordains and accomplishes the atonement primarily to manifest his glory. In the work of the cross God is glorified by maintaining his perfect justice while simultaneously being merciful to sinners. This is in addition to the glory God receives for formulating the plan of salvation and then realizing that plan by taking his wrath upon himself.
Soli Deo Gloria and Sola Gratia combined speak to the positive aspect of our salvation, or why salvation is all of God. Soli Deo Gloria relies upon Sola Gratia to establish the grounds upon which we are saved. Specifically, salvation is grounded entirely in God’s unrestricted favor. God receives all the glory in the act of salvation because it is his free gift. If salvation were in some sense necessitated God would not receive glory for being gracious, as the atonement would simply be what ought to have been done. Instead Sola Gratia calls for ascribing glory to God in a supreme way as He has gone above and beyond the “call of duty.” Soli Deo Gloria informs Sola Gratia by giving the reason that salvation is a free gift. God specifically structured salvation so that it was all of him to the end that he would receive all the glory for its accomplishment.
Soli Deo Gloria and Sola Fide combined speak to the negative aspect of our salvation, or why salvation is none of man. Soli Deo Gloria relies upon Sola Fide to assert man’s utter lack of contribution to his own salvation. Salvation is all of faith and none of works. Further, Sola Fide offers the reason for which this can indeed be the case, in particular an alien righteousness. If righteousness is not our own, and acquiring salvation is done through the empty hand of faith, then man has nothing to offer. Soli Deo Gloria informs Sola Fide by again reasoning why God has made this to be the case. Man has been particularly excluded from contribution in order that God might receive all the glory. If man had some contribution then he would have some grounds to boast in, and therefore a reason to receive some glory. Sola Fide strips man of all grounds of boasting and consequently all basis to glory in himself.
While there is certainly some unique truth in each of the Solas, they enjoy substantial overlap. This overlap is what makes them a strong and unified system of truth. Instead of loose and fragmented doctrines, we have in the Solas a central idea and motive. Soli Deo Gloria gives the other Solas purpose and direction so that indeed all things may be to the glory of God.