Comparison (using Ellipsis)

Question

I am trying to figure out when do we need to use an action verb explicitly and when can we omit it using the (ellipsis concept). For Example:

• John is taller than Jim [is] (I understood that here is can be omitted)
• John left earlier than Jim [did] - is it ok to omit the word 'did' - if not, why?
• Maple trees shed their autumn leaves earlier than oak trees - Is this correct?

Answer 1

In all these cases, the verb can be omitted in its second instance, and usually is more in line with contemporary English usage.

That is:

• John is taller than Jim

is "better" than:

• John is taller than Jim is

unless you are deliberately repeating the "is" for poetic or rhetorical emphasis.

However, there is an important point to note.

Suppose you are using a pronoun for the second of the two nouns in this construction. Then it is important to note that:

• John is taller than he

is actually more "grammatically correct" than:

• John is taller than him

but nobody uses the first form nowadays; it would be considered quaintly archaic, and mark one out as a foreigner who has learned English well and precisely from a text book a century old. Everybody uses the "him" form in this context. Who knows why? Linguistic drift of some kind.

On the other hand, and this is important:

• John is taller than he is

is correct, and does not sound archaic and false at all.

Go figure.

Answer 2

In languages that still use the inflected cases system, nominative is considered the only subjective case — so John, as the subject of the first clause of the comparison in the elliptical version has to be in the nominative: He. But The second clause of the comparison, whether it depends on a preposition such as "than" or not, comes in one of the other grammatical cases: ablative, genitive, accusative depending on the language. Given that English preserves the accusative for the personal pronoun, it is natural to apply that rather than the subjective "I".

Unless, that is, the second clause is a whole sentence ("...than Jim is", in which case "Jim", being the subject of the verb, can be replaced by "he".

Answer 3

The logic of the constrictions you give depends on what I see as “compared switchable subjects”. In each example two sentences are implied. John is tall ; Jim is tall. John and Jim may be switched between the implied sentences. Additionally, there is a comparison of the implied sentences: who is taller?

The logic is clear and the meaning is clear and unambiguous, making the grammar correct.