The Church Fathers on the Atonement
I have always been particularly interested in seeing what the theology of the Christian Church of the first 500 years was (in particular the parts of it that spoke Greek and so read the bible in their native language), and in understanding how they viewed the atonement. To that end over the last several years I have read most of the writings of the major and minor church writers from this period and read a dozen or so scholarly works on the subject giving both overviews and detailed analyses of the writings from this period. I was and am particularly interested in focusing on and seeing how each Father understands the work of Christ, what they saw Christ as achieving, and how that fitted in with their scheme of salvation. It was and still is my belief that it is extremely unlikely that the apostles failed to pass their ideas on to the succeeding generations, and thus seeing what these later Christians believed and teach in their voluminous surviving writings is a useful tool to help understand the New Testament.
It turns out that the writers from this period teach quite strongly various views of the atonement, and they are Ransom from Satan, Moral Exemplar, Christus Victor, and Recapitulation. What is not in that list, of course, is Satisfaction and Penal Substitution. Credit is of course commonly given to Anselm in the 11th century for his invention and popularisation of Satisfaction in his work "Why God became Man", which is an interesting read as an example of Scholastic Theology - he attempts show that a person sitting in their armchair at home could use pure reason to derive the existence of God, the need for Christ to die, and how the atonement worked. Anselm gave a critique of one version of the popular atonement model of Ransom from Satan, and in its place explained a full and complete Satisfaction model. Arguably Anselm did not invent the Satisfaction model from scratch, and perhaps up to 500 years earlier some of the ideas related to it can been seen as present in some writers of the Western Latin tradition of which he was a part. However he was definitely the first to give it a full and complete explanation, and also represents the point of turning in popular Latin Christian thought away from Ransom-From-Satan and toward a Satisfaction view.
Over the next five centuries, as society changed, the Satisfaction model underwent gradual changes. So, instead of being couched as Anselm had done, in an analogy with Feudal lords demanding recompense for their dishonour, it became couched in a judicial analogy with a just judge demanding punishment for a crime. Similar, but slightly different - in Anselm's version there doesn't really have to be punishment, only appropriate payment given which can involve perfect obedience rather than any form of punishment. Thus by 1600 or so "Penal Substitution" as it was now called was the dominant view of the atonement among the masses of conservative Western Christianity. Notably Anselm had written in Western Latin, so his ideas had never influenced the Greek Eastern part of the church who never held anything remotely like Satisfaction or Penal Substitution.
I am inclined to take the view that this historical evolution of Christian thought is the single strongest and most compelling evidence against Penal Substitutionary atonement. Namely its virtually complete absense in the Greek Christian writings of the period 100-500AD seems pretty decisive. If the apostles taught Penal Substitution as a central part of their gospel, then it seems almost entirely inconceivable that the generations that came after them and spoke the same language had, worldwide, managed to universally forget the major and central part of the gospel and replace it with something else entirely.
Origen, for example in his basically systematic theology called "On the First Principles of the Christian Faith" written ~230AD manages to totally fail to mention Penal Substitution, but does make extensive mention of a Moral Exemplar view as being what Christians teach. Irenaeus, a missionary to France writing ~180AD gives all sorts of imagery for the atonement that has scholars struggling to work out whether he was teaching Recapitulation or Ransom for Satan, but he certainly wasn't teaching anything remotely close to Penal Substitution. Justin Martyr, a Christian Philosopher living in Rome, in his "Defenses of Christianity" written in 150AD manages to not mention of Penal Substitutionary atonement despite talking about the core Christian doctrines, and he is widely regarded as the first post-biblical Christian writer to clearly explain and teach the Ransom from Satan view. Eusebius in his almost systematic theology "Proof of the Gospel" written ~310AD teaches Moral Exemplar pretty clearly. Athanasius' fairly extensive treatise on the atonement about the same time is widely regarded as the clearly example of teaching Recapitulation.
In short, we find a variety of atonement theories taught in the first 500 years of Greek Christianity. We also find Penal Substitution very absent, and glaringly absent in the places and writings we would most expect it to be if these Christians held anything remotely approaching modern views. But of course, they did not hold modern views. They didn't hold to original sin; they endorsed free will extremely firmly; they endorsed extremely firmly that the acts of humans could make them righteous before God; and they taught a final judgment according to one's life and character. Interestingly the views of atonement that they taught (apart from Moral Exemplar) had no connection whatsoever with causing humans to attain a positive final judgment by God - Ransom from Satan, Christus Victor and Recapitulation has the similarity that the "problem" they give a "solution" to has nothing whatsoever to do with whether humans go to hell or heaven (Recapitulation is about making there be a resurrection and not annihilation upon death, and the other two are about defeating Satan).
I consider these facts to be easily the clearest and most definitive evidence against holding a view of Penal Substitution. It is a modern doctrine which has evolved over the course of comparatively recent centuries and was not taught in the period of 100-500 in Greek Christianity. If we think we can find it in the bible we are therefore probably kidding ourselves, since those native Greek speaking Christians who lived with the same culture, in the same world, with the same language as the apostles never saw it as present in the same bible that people today claim to find it in.
Now of course, when confronted with this evidence the response of many Evangelicals is disbelief - "that just CAN'T be true!" The results tend to be amusingly sad, because they are sure they must be able to find Penal Substitution in those writings if they look hard enough, so they go off and search through these writings they know nothing about until they find a paragraph that's ambiguous enough that they can read Penal Substitution into it out of ignorance if they try. Thus we end up with moronic statements like "the following Fathers taught penal substitution" followed by a cite of five ambiguous paragraphs in the works of writers renowned for other views of the atonement. They don't seem to realise that even if they find a dozen paragraphs that clearly teach Penal Substiution it is still irrelevant - because we are talking about a collection of works that are on the order of 50,000 pages all up. To find only a dozen mentions of Penal Substitution in a collection of writings of that volume is to simply prove that these writers placed virtually no value whatsoever on the idea. If modern Christians mentioned Ransom from Satan, Recapitulation, Christus Victor and Moral Exemplar in 20% of all the paragraphs they wrote on Christianity, and Penal Substitution in 0.001% of their paragraphs, then it wouldn't take a genius to figure out that their core doctrines were not Penal Substitution.
But I have issues with the fact that these people think they can simply cite a paragraph from deep in the bowels of works they have not read, by authors they've spent no time trying to understand, and claim it teaches Penal Substitution, when in fact the authors held none of the theology necessary for a Penal Substitutionary framework, and the paragraph is not intending to say anything close to what they get out of it. This has been brought to my attention because apparently the recent Pierced For Our Transgressions book does this... no doubt the authors trawled through 20th century Evangelical apologetics and harvested all the misguided citations of the "Church Fathers advocating Penal Substitution" that they could and said "Look! They believed what we believed". I'm sure it looks convincing to people who have never read any of the Church Fathers writings. For those of us who've read lots of them, it's hilarious. Some of the names on their list are particularly ridiculous. "Athanasius" for example apparently taught Penal Substitution - is this the same Athanasius who's famous for his advocation of Recapitution? Why yes it is. "Gregory Nazianzus"? The same Gregory Nazianzus who explicitly rejects the possibility of the atonement as targeted at God in another one of his works? Why yes it is. "Justin Martyr"? The same Justin Martyr who's one of my favourites? Yup... apparently I hadn't spotted that "clear" statement of Penal Substitution in the middle of one of my favorite authors. Their citations might look remotely plausible to the ignorant, but they have those of us who know our stuff rolling on the floor laughing.