Historically, one strategy that Reformed theology has used to combat the exegetical arguments of Lutheranism is the philosophically based maxim that the "finite is not capable of the infinite" (finitum non capax infiniti). It goes without saying that as a result Lutherans have frequently charged the Reformed with a certain degree of crass rationalism. This principle has no basis in Scripture, and demonstrably contradicts the teachings of Scripture. That this later difficulty attends the Reformed insistence on this maxim has been made abundantly clear from exegetical arguments made above.
One cogent explanation for the Reformed’s easy acceptance of philosophical rationalism relates to the theological antecedents of the southern Reformation in the philosophical frameworks they inherited from the earlier scholastics. It should not go unnoticed that Zwingli was a student of the Thomas Wyttenbach at the University of Basel. Richard Muller has also shown that the majority of the Reformed theologians of the first generations were trained in the via antiqua, which taught that there was a definite continuity between human and divine reason. By contrast, Luther matriculated at the University of Erfurt where the theological soup du jour was via moderna, with its characteristic emphasis on the discontinuity of human and divine rationality.
On another level though, it is rather surprising that for all their rationalism the Reformed would adopt such a clearly self-contradictory argument. In other words, simply taken from the perspective of human reason, the argument that the finite is not capable of the infinite is a blatant absurdity.
In order to see this, it is important to observe what is meant by the Lutheran capax. As the Swedish Lutheran theologian Gustaf Aulén notes, the Lutheran argument is not that the finite has some sort of inherent capability of containing the infinite, but rather that the infinite God is capable of communicating himself to the finite. Seen from this perspective, the Lutheran teaching does not entail positing a sort of intrinsic capacity of creation for infinite self-transcendence, in the manner that we might find in later German Idealism. Rather, the accent falls exclusively on the capacities of the sovereignty and power of the infinite creator God. Hence denial of the Lutheran capax does not somehow keep creaturely capacities within their own proper range, but rather openly denigrates divine capacities. As David Scaer has noted, if the infinite were not capable of communicating itself to the finite, it would by definition not be infinite. That is to say, if the infinite is truly infinite, then it must logically contain an infinite number of possibilities and one of these possibilities must be being contained by the finite. Seen in light of this, that the Reformed would make this argument, especially with their emphasis on the infinite power and glory of God is extremely puzzling.