Philosophy was an “add-on” to theology for the post-Reformation writers. It was “an aid to learning” (“ancilla”) but it did not contain the substantive material that was to be considered when evaluating “theology proper” (i.e., issues surrounding the Doctrine of God, etc.). In other instances, it was found, some philosophies were outright hostile to Christianity.
The Reformation, broadly understood, was not at all a philosophical movement—nor was the early orthodox extension of Protestant theology a fundamentally philosophical development marked by commitment to a particular philosophical perspective.
The simplest and best description of the philosophical perspective (or perspectives) found among the Reformed thinkers of both the Reformation and the early orthodox eras is “eclectic.” Still, there remains a significant philosophical background to the Reformation, a background that is not exhausted by medieval patterns but that also follows out patterns in the Renaissance.
The eclecticism of the Reformers and their successors, moreover, ought not to be understood as an incoherent philosophy, but rather as a philosophy drawn out of a multitude of sources both classical and medieval, modified by a Renaissance reading of texts, and guided by the desire to develop a pattern of rational argument that could serve theology in an ancillary position.
This pattern or ethos of reception in turn determined the relationship of various Reformed thinkers to the varied philosophical options of the era—from one perspective, much of the philosophy of the age can be described as a modified Aristotelianism, but, if the question of antecedents is raised in detail, there are Stoic and Platonic or Neoplatonic elements in the Reformed thought of the era and there is an interest in the ancient truths found in the Hermetic writings, viewed by the thinkers of the sixteenth century as dating from the time of Moses and, at the same time (ahistorically!) as fundamentally Platonic in implication.
This use of philosophy, including the interest in the Hermetic literature, indicates, moreover, a continuity of discussion throughout the late Middle Ages, Renaissance, and Reformation eras.
Given these sources of philosophical thought in the sixteenth and seventeenth centuries, the references found in sixteenth and seventeenth century Reformed thought to Aristotle, Epicurus, various Stoic thinkers (not to mention Arius and other heretics of the patristic era) must not be taken merely as pro forma references to ancient philosophical and theological options.
Rather, they are references to philosophical and theological options found in the historical context of Reformation and post-Reformation thought. The debates over Aristotelian, Epicurean, and Stoic options, therefore, are debates over the assimilation, adaptation, or rejection of living philosophical and theological options, and over the identification and adaptation of a suitable ancilla for the theological enterprise.
They are also debates that led to the severing of traditional Christianity from the dominant rationalist philosophies of the eighteenth century, given the rootage of much Enlightenment rationalism in the revived classical, indeed, pagan philosophical models of the Renaissance.
Muller, R. A. (2003). Post-Reformation Reformed Dogmatics: The Rise And Development Of Reformed Orthodoxy; Volume 1: Prolegomena To Theology (2nd ed., pp. 67–68). Grand Rapids, MI: Baker Academic.
Muller has something more to say about this, and it leads into an event that I’ve written about, The Decline and Fall of Reformed Churches in America. While in some senses, some philosophies were found helpful to Christianity, in other senses, they created a hostile and virulent environment.