Greece had not been enslaved

Question

The following is an extract from Frankenstein by Mary Shelley. Is the "had not been" correct? Should it have been "would not have been"?

"A human being in perfection ought always to preserve a calm and peaceful mind, and never to allow passion to a transitory desire to disturb his tranquility. I do not think that the pursuit of knowledge is an exception to this rule If the study to which you apply yourself has a tendency to weaken your affections, and to destroy your taste for those simply pleasures in which no alloy can possibly mix, then that study is certainly unlawful, that is to say, not befitting the human mind. If this rule were always observed; if no man allowed any pursuit whatsoever to interfere with the tranquility of his domestic affections, Greece had not been enslaved; Caesar would have spared his country; America would have been discovered more gradually; and the empires of Mexico and Peru had not been destroyed."

Answer 1

This seems to be an archaic form of the subjunctive; the sentence is introduced with if, indicating an irrealis condition. I found a paper by Éva Kovács in the Eger Journal of English Studies IX (2009) 79–90, "On the Development of the Subjunctive from Early Modern English to Present-Day English," which asserts the following:

As for the past subjunctive, it is used in apodoses (main clauses) of unreal conditionals, which is highly literary and was already a rather pompous archaism by the early nineteenth century and would be would be normal (Denison 1998:163):

(21) But it were better not to anticipate the comments to be made. (1948 TLS 23 (10 Jan))

The past perfect subjunctive is used similarly, which is illustrated by the following example, in which had been stands for would have been in Present-Day English:

(22) It had been easy for me to gain a temporary effect by a mirage of baseless opinion; (1871–2 George Eliot, Middlemarch 201)

Answer 2

We need to remember that, despite her undoubted intelligence and acquaintance with well educated and eloquent people, the author had little or no formal education, and her prose style suffers as a result. Here she is using "had" to indicate a subjunctive, a statement contrary to fact or belief. The form is still used with an inversion

Had I known ...

but is, at least in the US, old fashioned. And it is obviously used commonly without inversion and with a preceding "if"

If I had known ...

But I must admit that I have never seen anything like this concatenation of verb forms. The meaning is

If all observed the rule that we permit nothing to disturb our domestic affections, then Greece would not have been enslaved, Caesar would have spared his country, and America would have been discovered more gradually, thereby preventing the destruction of the empires (civilizations?) of Mexico and Peru.

The above is still a long, convoluted sentence, but it is comprehensible. (Whether you find it persuasive is a different issue.)