Neuter adjectives with no obvious antecedent

Question

Two questions about the following text:

Hac ratione creato homini legem posuit, quam praestari ab eo non tantum possibile, sed & aequissimum erat, addita proinde comminatione mortis si eam transgrederetur.

He laid down a law to the man who had been created in this manner, which was not only possible to be fulfilled by him but was also most equitable, and hence with the added threat of death if he would transgress it.

1. "Possibile" and "aequissimum" are neuter adjectives, but there is no neuter noun. Are they meant to modify the verb "praestari?" Like if "praestari" were to be rendered a noun?

2. Why is "quam" in the accusative when it is not the direct object of any verb? I'm guessing it refers back to "legem."

Answer 1

The missing neutral noun is praestari.

Infinitives can act as nouns. They are neutral and undeclinable. They are often objects but can also be subjects:

Errare humanum est.
To err is human.

When they are the subject, they rarely have a subject. But it is possible, and in that case, their subject is in the accusative.

Te venire pergratum est.
Your coming is very welcome.

Terram esse rotundam certum est.
It is certain that the earth is round.

(I picked these examples from old Latin grammars I found on Google books such as this one—but I would love to see a real classical example.)

With that in mind, in your sentence the core is: (legem) praestari erat possibile et aequissimum: It was possible and most just that the law was being fulfilled [= obeyed, I assume].

Answer 2

1. "Possibile & aequissimum erat" is an impersonal sentence, which can be translated in English as "it was possible and most fair", but which needs no such pronoun in Latin.

2. What was 'possible and most fair' is here expressed as an accusative-infinitive, with quam (indeed referring back to legem) and praestari.

So "... legem posuit, quam praestari ... possibile ... & aequissimum erat" is literally: *"... He laid down a law, which it was possible and most equitable to be fulfilled". Which is to say: It [impersonal] was possible and most equitable that it [the law] be fulfilled.

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However, in English, we can't use an acc-inf with an impersonal sentence. "I want the law to be fulfilled" is correct, but *"It is possible the law to be fulfilled" is not. We can insert 'for' before 'the law' ("It is possible for the law to be fulfilled") or we can use a that-clause ("It is possible that the law be fulfilled"), or perhaps both "It is possible for the law that it be fulfilled" (?). But for some reason these solutions look strange in a relative clause: "A law, (for) which it is possible that it be fulfilled" (?) or "A law, (for) which it is possible to be fulfilled" (?).

Substituting the impersonal subject is also wrong: both *"The law was possible to be fulfilled." and *"The law, which was possible to be fulfilled."

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So I'm afraid the best way to handle this sentence is to turn the passive into an active and turn the accusative from the subject of an acc-inf clause into a simple object of the infinitive: "... He laid down a law, which it was possible and most equitable to fulfill" (as if the Latin said "legem posuit, quam praestare ... possibile ... & aequissimum erat").