I guess what is perplexing me right now is that the claim that Chalcedon upheld both "one nature" and "two natures" contradicts everything I thought I knew about Chalcedon and the Chalcedonians up until now.
The Definition of Chalcedon has only "in two natures," and nowhere mentions "one nature," or "of two natures."
St. Dioscorus wanted the Definition to say "of two natures," and from what I understand he might have signed onto Chalcedon had the Definition said that (someone correct me if I am wrong here.) But "of two natures" was rejected and only "in two natures" was used.
"One nature" was condemned at Flavian's Synod. The bishops at Ephesus II overturned Flavian's Synod (partly because condemning "one nature" would have condemned St. Cyril,) but then Chalcedon overturend Ephesus II.
I know I've read things written by EO's (including threads here at OCnet) that condemn "one nature" as being per se heretical.
For centuries Chalcedonians have called the OO's "monophysite" (meaning "one nature.") That term was always used pejoratively and was equated with heresy.
Although I cannot say that I have read the entire minutes of Chalcedon (I haven't the strength

) I've read significant portions of it, and I never ran across anything affirming or supporting "one nature" or "of two natures."
So you guys can imagine my surprise when recently a Chalcedonian told me that Chalcedon approved of both "one nature" and "two natures." Moreover, he indicated that EO's as a whole have no problem with "one nature," and actually do use it approvingly.
It just didn't make sense to me.
But I am willing to be proved wrong. I just need someone to show me where in Chalcedon "one nature," or "of two natures," was approved. I also would like to see something written by a Chalcedonian--an article, sermon, anything like that--which approvingly uses "one nature" to describe the union of divinity and humanity in Christ.