What use is this ablative in?
Mox Porsena magnis cum copiis Romam venit et urbs ipsa summo in periculo erat.
My best guess is the ablative of manner.
Thank you.
I’m not sure I follow you. What would be the meaning with an ablative of manner?
summo in periculo…
It’s the ablative with the preposition in, so that controls the usage. Now, in has a prodigious range of usage with the ablative, most (but not all) of which may be rendered in English with our cognates “in” and “on.” If I had to pick one here, I’d say:
40 (expr. conditions under which an action or situation occurs) In, amid (given circumstances).
Glare, P. G. W. (Ed.). (2012). Oxford Latin Dictionary (Second Edition, Vol. I & II). Oxford: Oxford University Press.
The ablative of manner is used with cum or without a preposition, never with in.
The phrase summo in periculo means in great danger, so in this case the in + abl. responds to the English preposition in. I do not see any need to classify this usage, but maybe others can chime in.