In the American version of morphology, (you still haven't addressed the question of why your understanding of 'morphology' is rather different from that given in British and American dictionaries.) as I know it, the infinitive always is preceded with "to" -- even the past infinitive "to have sung". The word "can" in "can sing" is considered a "helping verb" (quite different from other verbs, in that it does not have an infinitive form. One does not say "to can", but rather "to be able to") helping a the "main verb" "sing", which we would not call the infinitive.
Well, we have a fundamental difference of opinion here. Most grammarians, British and American, that I have read do consider 'sing' in "I can sing" to be an infinitive. If you think it's not an infinitive (or 'bare infinitive' as it's sometimes called), then what do you think it is?
We would probably say something similar about "Let's go", calling it the imperative mood -- somewhat similar to "allow us to go".
Is it of any value to consider that English has an 'imperative mood'?
It just happens that 'let' is followed by the bare infinitive, and that 'allow' requires 'to' before the infinitive, just as some French verbs require [FONT="]'à'[/FONT] and 'de'.
I am aware of the "a", "de", and "zu" that you spoke of, but translating "parler" as "speak" would not distinguish it from "parle, parles, parlent" etc. In constructing a conjugation, then, we give, as a title, the infinitive form of the verb, e.g. the conjugation of the verb "parler". je parle, tu parles, il parle, nous parlons, etc.
Frank, we cannot analyse English grammar by talking about what happens in French. One of the problems with the English grammar that was taught until the 1960s (indeed, until today in some places) is that writers tried to apply the rules of Greek and Latin grammar to English. People used to speak of nominative, vocative, accusative, genitive, dative etc cases in English nouns. This is rubbish. Apart from a possible 'possessive' case (with the 's/s' suffix), English nouns do not show case. With some pronouns, it is possible to speak of an 'objective form' but the word 'case' is irrelevant. The English word 'him' can be used to translate an accusative, dative or ablative Latin equivalent; that does not mean that English has these cases..
The experience of teaching English as a foreign language must be so different from teaching, say, German to native English speakers. In some ways English is SOOO simple.
Tell that to people trying to learn English!
I did, for many years, teach German to English speakers, so I do have experience of both sides. [...]
So often I have heard people say that they only understood English grammar when they studied Latin. The use of "traditional grammar" here, is currently very much out of fashion. I think Chomsk[STRIKE]i[/STRIKE]y is partly to blame. I buck that trend.
Fine - if you want to teach 'grammar'. I have never actually seen much point in that. I doubt whether Shakespeare could have told a predicate from a preposition, but that didn't stop him writng a couple of good lines of verse from time to time.
I would not want to tackle German without prior knowledge of gender, case, number, tense, mood, relative pronouns, antecedents, irregular verbs, etc.
Well, most Germans manage it pretty well until they go to school, and until about a couple of centuries ago, most of them didn't go to school. Until fairly recent times, most non-German merchants, servants, shippers, hoteliers, etc managed to converse with their German colleagues, masters, clients, etc without the faintest idea of what a 'mood' might be. In some parts of the developing world today, there are illiterate people who can communicate happily in four or more languages.
I hope this discussion can be continued in good spirit.
Well, I am in very good spirits.