We then would seem to understand the same texts differently.
The notion that the Biblical understanding called penal substitutional atonement to be a theory is from what I understand is an early 20th century invention.
It is not a matter of understanding the same texts differently.
Christ died for us. I say this means Christ died for us. You say it means Christ died instead of us. You remove the word "for" ("on our behald", I'm our intrest", or "as our representative") and replace it with "instead of".
We read "Christ bore our sins bodily" and "He shared our infirmity". I understand this to say that Christ bore our sins in His body, He shared in our sickness. You read it to say "Jesus experienced God's wrath instead of us".
Were it simply a matter of interpretation this would be an entirely different discussion. We can debate interpretation (like the meaning if "baptism", of "logos", etc.
But you are adding to Scripture what is not in the biblical text and call it "teaching". How can you test the teaching if not by the text of Scripture?
The reason it is called "theory" has nothing to do with the 20th century. There have always been different understandings of the Cross.
Penal Substitution Theory has been around for about 700 years. Part of the reason many call it theory is because it is one of many views (they lump all views as theories, including some that are strictly interpretations and others that are literal theories. Some call it theory because it is a relatively new understanding. Of the major views, Penal Substitution Theory is the newest to Christianity (I would not call the "Bloodless Atonement" of Denny Weaver a major view....yet, anyway).
But the reason Penal Substitution Theory is literally a theory is because it incorporates extra-biblical ideas into its construction. You can quote verses, but they are held together by a moral philosophy that did not exist until the Renaissance.
