Some verbs have the same spelling for adjective and past participle. How do you differentiate between "sein + adjective" and "sein + past participle"?
For example:
Die Historiker sind auf die Erforschung von Gegenwart und Vergangenheit konzentriert. (adjective)
Ihr ganzes Wesen war darin konzentriert. (stative passive)
Predicative adjective and stative passive are basically two ways of looking at the same expression. There is no formal difference btween them. In both cases we can reform the sentences to give an attributive adjective:
Die auf die Erforschung von Gegenwart und Vergangenheit konzentrierten Historiker …
Ihr ganzes, darin konzentriertes Wesen …
The only tidbit of a clue you may get is whether a sentence can be rewritten in a dynamic passive form:
Ihr ganzes Wesen wird darin konzentriert.
This kind of works.
Die Historiker werden auf die Erforschung von Gegenwart und Vergangenheit konzentriert.
This doesn’t work, so probably the stative passive definition is not applicable here.
See also this, slightly related answer of mine.
I have no real rule but I thought about it a little and here is something that might actually work:
Try to cross it out and see if the sentence does still carry its meaning/ if it still sounds plausible:
Die Historiker sind auf die Erforschung von Gegenwart und Vergangenheit
konzentriert.
→ Clearly sounds weird, something is missing.
Ihr ganzes Wesen war darin
konzentriert.
→ The basic message can still be understood albeit we lose some information which is to be expected after deleting an adjective.
Have a try and let me know if it works!
