What is the function of ‘before clause’ in the sentence？

Question

When I was reading the book The Giver， I read the following sentences.

There was a time, actually—you’ll see this in the memories later—when flesh was many different colors. That was before we went to Sameness. Today flesh is all the same, and what you saw was the red tones.

As for the bald sentence, I am not sure the function of the 'before clause'. The structure of the sentence, according to my understanding, is 'Subject+be+completment'. But when I'm googling， I found that before clause is used as adverbial clause.

Answer 1

You're right. The preposition phrase is a complement by virtue of being obligatory

Adverbials (or adjuncts) are always optional.

There are also "obligatory adverbials" but the term is not used in modern grammar; they belong to the category of complement.

Answer 2

There was a time, actually—you’ll see this in the memories later—when flesh was many different colors. That was before we went to Sameness. Today flesh is all the same, and what you saw was the red tones.

That is a demonstrative pronoun that refers back to the aforementioned time, the time when flesh was multicolored.

That [time of multicolored flesh] was before [i.e. it predated the time when] we went to Sameness.

before is complemented there by the finite clause "we went...". Such a clause, with its tensed verb, expresses the idea that an action takes place in time, and this makes it a valid complement for before, which expects a point in time reference of some kind (when it has its temporal meaning).

For example:

She will arrive before {noon}.

He washed his hands before {he ate}.

But it need not be a tensed verb.

She visited her cousin before {going to the movies}.

P.S. The temporal prepositional phrase resolves to a time-reference.

That [time of multicolored flesh] was {WHEN}.

Answer 3

A clause introduced by "before" can be used as an adverbial clause.  It doesn't have to be.  It can also be used as an adjectival clause.  In the example sentence, it is adjectival.  Consider this example: 

The time when flesh was many different colors was a time before we went to Sameness. 

Here, the function of "before we went to Sameness" is the same as the function of "when flesh was many different colors".  In the sentence above, they each directly modify an instance of the noun "time". 

 

In the original example, it still modifies an instance of the word "time"*, but it does so indirectly, as licensed by the copula "was" and indicated by the demonstrative "that". 

Yes, the structure of the sentence in question is subject / verb / complement.  More specifically, it's subject / copular (or linking) verb / predicative adjectival subject complement. 

Different frameworks label things in different ways.  Traditional grammars are more likely to label this "before" as a subordinating conjunction.  Modern grammars are more likely to label this "before" in the same way as they label the "before" of "before noon" -- as a preposition. 

 

Q:  Is "before we went to Sameness" a predicative complement in the example sentence? 
A:  Yes, it is.  It acts as the argument of the predicating verb "was". 

Q:  Is "before we went to Sameness" an adjectival complement in the example sentence? 
A:  Yes, it is.  It acts as a modifier of the subject.  A nominative complement would act as a separate reference to the subject's referent. 

Q:  Is "before we went to Sameness" a subject complement in the example sentence? 
A:  Yes, it is.  The constituent that it modifies is a subject, not an object.  Specifically, it modifies "that".

Q:  Is "before we went to Sameness" a complement in the example sentence? 
A:  Yes, it is.  We can identify the constituent that licenses this constituent.  In this case, "before we went to Sameness" is an argument of the verb "was".  We can also identify the constituent that this constituent complements.  In this case, "before we went to Sameness" complements the subject "that". 

_______________ 

* If we wish, we can go a bit further down the rabbit hole: the adjectival clause modifies an already-modified instance of "time", since the demonstrative "that" refers to the entire content of "a time when flesh was many different colors".

Answer 4

There was a time, actually—you’ll see this in the memories later -- when flesh was many different colors. That was before we went to Sameness. Today flesh is all the same, and what you saw was the red tones.

The "before" expression is not a clause but a preposition phrase headed by the preposition "before" with the declarative content clause "we went to Sameness" as its complement. The PP is functioning as subject-oriented complement of "be".

The primary meaning of "before" is temporal; more specifically it heads an expression whose temporal location is prior or subsequent to that of some other situation(s).

The demonstrative determiner "that" has the entire preceding clause (excluding the parenthetical supplement) as antecedent.

Here, the function of the PP is complement of "be". It’s not a predicative though since it doesn’t ascribe some property to the subject; rather, it locates the temporal situation of the embedded clause "we went to Sameness" as being subsequent to that described by the antecedent of "that".