Socinus could affirm that "Christ died for our sins" but not in the sense of substitution and satisfaction. However (as then so it is now) his affirmation of believing that verse in 1 Corinthians 15 muddied the waters because the sense that he assigned to that statement could only be described as in effect "another gospel." The impression this gives of course is one of orthodoxy, the reality, however, is in fact a denial of orthodoxy. And the effect of this equivocation is to confuse the issue and to risk both confusion in the church and the facilitating of the spread of error.
Someone might comment 'Didn't he say that he believed that "Christ died for our sins?" Then why are you giving him such a hard time? He's not unsound if he believes that.' But it is not just what he says when he uses that phrase, it is what he means by those words that really matters ("Christ" and "for" being interpreted by Socinus in radically different ways).
The very same equivocation was made recently by one well known author who affirmed his belief that "Christ died for our sins" but who also consistently vilifies and undermines the doctrine of penal substitution. The impression is given is one of agreement because of the use of a critically important phrase in Scripture that defines the gospel, but it is only an impression. That is what you call an "empty orthodoxy."
What I soon found as I was reading about these seventeenth century debates was a striking continuity not only of the theological positions available but also of the arguments put forward by the protagonists on all sides. Arguably even the concessions made to opponents by those in favour of penal substitution were the same then and now. It was a further reminder, if I needed it, of the value and importance of historical theology when assessing contemporary controversies.
Carl Trueman has a superb recent essay on James Buchanan's The Doctrine of Justification where he makes this powerful plea not to ignore the history of debates on justification:
Karl Marx once commented that Georg Wilhelm Friedrich Hegel had noted that all historical facts and personages occur twice; but, he added, Hegel failed to note that the first time this was as tragedy, the second as farce. His comment surely applies by way of analogy to great theological duscussions as well, and only by taking history seriously can such tragedy and farce be avoided.Carl R. Trueman "A Tract for the Times: James Buchanan's The Doctrine of Justification in Historical and Theological Context," from Anthony T. Selvaggio [ed.], The Faith Once Delivered: Essays in honor of Wayne Spear, p. 61-2
Thus I offer in closing these final comments as a historian's passing shot across the bows of modern theologians--systematic, biblical, and all points in between--who pursue their calling with ne'er a glance at history: if they wish to avoid the tragi-farcical options of either reinventing the wheel or of privileging their own narrow interpretative horizons over those of the church throughout the centuries as reflected primarily in her creeds and confessions, they might do well to meditate on the fact that current controversies on justification are reminiscent in so many ways of the issues raised relative to this doctrine through the centuries, not least by the Tractarians of the nineteenth century.