I've been thinking about how some people have started accepting sentences like "I am taller than him", arguing that than could regarded as a preposition. Why could the same argument not be used about the conjunction and in cases like "Peter and me went home"?`

What do you think?

You're not getting me. "Than" has usually been regarded as a conjunction, but now more and more people think that it is ok to use "than" as a preposition. Why could we not do the same about "and." I know that "and" has traditionally been a conjunction, but since people use it as a preposition nowadays, why not call it one?

Think about "but". "But" is usually a conjunction, but in sentences like "Everyone but me went home." or "Everyone went home but me." it is a preposition.

My argument for "and" being a preposition is that people use it as one. People do say "Peter and me went home." Why should one insist that this is wrong when there are many other examples in the language of double word class membership when it comes to prepositions/conjunctions.

Hello again, Mask.
I musunderstood your question, but I see what you mean now.

Just like many other English words, "than" belongs to more than one class. It is a preposition in sentences like "She is taller than me", and it is a conjunction in sentences like "She is taller than I (am)."
In other words, "than" is regarded as a preposition when it is followed by an object, and it is a subordinating conjunction when it introduces a comparative clause (or a structure that can be expanded into a clause).

I also agree that "but" is mostly used as a conjunction, but in certain constructions it acts as a preposition. It can also be an adverb and a noun.

"And", however, is different. unless it is used in initial position, to join two sentences, it is always a conjunction. And that is not capricious really. "And" is a conjunction because you use it, as was said before, to join two words, phrases, clauses, etc. that have the same grammatical status.

You can say "You and me". But that construction will be correct only if it appears in the right place in an utterance. Unlike other grammars -such as that of my mother tongue- English grammar is based mainly on word order. There are categories (word classes, structures, etc.) which you can use in a certain position in a sentence but which will be incorrect if you move them to a different position... unless you change their form.

Returning to "You and me", it wil be correct if you use that construction in object position for example, but it will be incorrect if you use it as subject. Why? Because "me" is the objective form of the pronoun "I", regardless of whether or not you are using "and".
You say "you and I speak English", and you say "English is spoken by you and me".
There is no doubt that "and" is a conjunction in the first example. Now, if you look at the second example, you will see that "and" has exactly the same function as in the first one. Its function hasn't changed, so it is no necessary to think of a different category for that word. It is joining two words of the same grammatical status in both sentences.
"And" will not become a preposition just because the word that comes after it is an objective pronoun.

I don't know if this is clear enough or if it answers your question. I hope id is, and that is does, though.

Miriam