ergative

For instance, most so-called ‘ergative’ languages are actually a mixture of alignments, with parts of the grammar using ergative alignment, but other parts using accusative alignment.

For the purpose of inflicting severe bouts of pain in the rear orifice, give Basque (an absolutive-ergative language) or Georgian (a Kartveli language with the split ergative) a go.

A nitpick, but this is known as ‘neutral’ alignment, rather than ergative alignment.

There is actually a potential trace of an ergative system in Latin.

Ergativity is specifically when the transitive subject (‘ergative’ argument) is treated differently to the transitive object/intransitive subject, which are treated the same way (‘absolutive’ argument).

What about languages with ergative-absolutive alignment?

This is exactly the same pattern as in ergative grammar: the object of a transitive verb has the same case as a thing that is the subject of an intransitive verb.

I was under the impression that the unification of nominative and accusative case for neuters in Indo-European languages was indeed felt to derive from an ergative-absolutive distinction in proto-Indo-European.

I personally quite like Deal’s ‘ergative’ and ‘absolutive properties’ [0] as a first attempt; but I haven’t yet seen Lazard and Haspelmath, so I should look into that more.

We call the grouping of intransitive argument+transitive object the ‘absolutive’, and the transitive subject by itself the ‘ergative’; thus, a system like this, where the intransitive argument behaves the same as the transitive object, is called ‘ergative–absolutive alignment’.

I’ve definitely seen some speculation about PIE having been ergative at one point (or at least split intransitive), but I don’t know enough about it myself to have a strong opinion either way.

Some of those options people may realize without exposure to the particular languages, but others -- such as, say, ergative-absolutive alignment (not that I'm suggesting that's a good option to use) -- they won't.

English lacks a formal middle and there is a good deal of established literature on verbal aspects where the subject is not really the agent called "ergative".

Can you give examples of what a "ergative–absolutive alignment" looks like, or case-stacking?

> Can you give examples of what a "ergative–absolutive alignment" looks like, or case-stacking?

For example, proto-Indo European had Nominative Accusative alignment, and was highly inflected, but modern English is almost completely uninflected, and Hindi has Ergative-Absolutive alignment for some tenses.