“Iam filius noster nôn modo pede, sed etiam bracchiô aeger est”.
Another mental block - why ablative?
Paul.
Hi Paul
If you want to give it a name its the “ablative of respect”.
The ablative in pede aeger specifies the application of the term aeger. It answers the question “in what respect?”, hence sick “in respect of the foot”. That at least is how it’s described in LLPSI.
The margin note says pede aeger est = pedem aegrum habet.
Postscript : Allen and Greenough call it “The Ablative of Specification” and [it] " denotes that in respect to which anything is or is done."
https://dcc.dickinson.edu/grammar/latin/ablative-specification
Not sure it matters much what you call it.
“Tengo la pierna mala”.
“Ich habe die nase voll”.
Given my other languages, you’d think I’d have figured this one out.
Cheers.
Paul.
PS: I hadn’t noticed the margin note. This is bad - I’m not paying enough attention.
PPS: To be fair, it was on a different page.
So it looks simply like:
“His foot is poorly” vs “He has a poorly foot”.
Sorted.
Paul.
Yes the ablative occurred in an earlier line and so did the note.
“Itaque pedem aegrum habet nec ambulāre potest. Nec modo pede, sed etiam capite aeger est.”
So it looks simply like: “His foot is poorly” vs “He has a poorly foot”.
Do you really mean this?
I think this illustrates the pitfalls of translating into English, especially literally. “pede aeger est” means exactly the same as “pedem aegrum habet.” You don’t need to a draw a distinction where none exists. You wouldn’t translate “j’ai faim” as “I have hunger” you would say “I am hungry”, so apply that principle to Latin.
Well, yes. I speak Spanish every day without translating anything (although I am a translator). What I’m saying, is that at this stage of my learning, I need to know that to me they mean the same thing, as I’m not advanced enough to know the subtle differences. A bit like in these books we see stuff like “atque = et”. It’s close enough for us beginners.
BTW, being a translator does help to avoid the very pitfalls that you mention. No, I wouldn’t dream of translating “Ich habe die Nase voll” as I have the nose full and neither would I translate “Tengo la pierna mala” as I have the leg bad. Unfortunately, we will see lots of this sort of stuff, as people are using the pandemic as an excuse to not pay for anything. So lately I have no work and google is churning out rubbish translations which are being used even in mission critical situations. Scary stuff.
PS: An example:
But you have to read it in Spanish. It’s all about machine translations going wrong, so if you give it to san google it will come out as chicken soup.
I think we are at cross purposes, which isn’t good as I was trying to be helpful and appear to have been critical.
I was just trying to say there is no difference in meaning between “pede aeger est” and “pedem aegrum habet” so to give different literal English translations for the two phases isn’t helpful.
I am sorry to hear your translation work has dried up. But being able to read and speak a foreign language without translating in your head means you have a very clear picture of how one aims to read Latin. That gives you a head start on those who don’t have your experience with modern languages. 
Yeah, we do seem to have misunderstood each other a tad 
My 2 versions in English was to illustrate exactly what you say - that the same thing can be written/said in various ways in any language. But also that for a native speaker there can be subtle differences - a bit like how in Latin, word order, on the face of it, doesn’t matter, but once one digs a bit deeper, we can learn about stuff like emphasis. I don’t know if I’ll go far enough in my study of Latin to learn of any such nuances. For now I’ll just train myself to see those different constructions as the same thing
I think today’s latin study may have to give way to the piece I’m trying to learn on guitar (Fernando Sor).
Paul.