ch 36 fio - is it copulative?

[phil]

One of the exercises at the back is-
vos oramus ut discipuli acerrimi fiatis. We are begging you so that you might become very keen students.
I would have thought it should be discipulos acerrimos.

[benissimus]

Usually you won't see a direct object with a passive verb (except deponents). The concept is that you are talking about the same subject, so the two nouns (implied vos and discipuli) must be in the same case. So, just as in the active Facitis vos discupulos (You make yourselves students), in the passive it is (Vos) fitis discipuli. You usually only have to worry about this with fio and sum... usually

[Moerus]

'Fieri' is used like 'to be' with a nominative as a predicate. You can see 'become' as a dynamic action that becomes a static action in 'to be'.
E. g.: If you are becomming a father or a mother, one day you will be one.
In fact 'become' is the same verb semantically as 'to be', only 'become' stresses the dynamic vision of the idea, 'to be' the statis vision of that same idea.

In Latin 'fieri' is also seen as the passive of 'facere'. That's also a good way to understand why we put a predicate with it. With a passive you can't have a direct object, so don't use the accusative for that prurpose with a passive verb, neither with fieri, wich is seen as the passive of facere.
With passives like 'fieri' we use a predicate noun in the nominative.
The thing to know is that some verbs have an active form, but a passive sense (the opposite of deponents you can say). These verbs have the constructions of passive verbs. So we have to use a predicate noun instead off a direct object.
An other verb like this is 'Vapulare', wich is used like the passive of 'pulsare ...'.

Greetz,

Moerus