A proposed tool about the use of は and が and about the use of "the" and "a" in English

Question

UPDATE: Based on the discussion below, I now see that my proposal is not valid. But still, I want to make a clarification about the following proposal, anyway. Just please keep in mind that I'm keeping this modified version of the original question here simply for reference, and not to assert that it's correct, because I now know that it indeed is not nearly as correct as I was hoping.

I'm changing my original question below by replacing "indefinite/definite article" with "indefinite/definite modifier". Such a "modifier" could be an article, an adjective, or even an adjectival phrase. In "some cats like fish", "some" is an indefinite modifier. The same is true with simply "cats like fish", in which the lack of a modifying word or phrase is a plural manner of indicating indefiniteness, and in this case, no modifier is an implied indefinite modifier. Likewise, in "those cats like fish", "those" is a definite modifier. In my proposal (which, again, I now realize is indeed not valid), replace references to "A" and "THE" as follows ...

MODIFIED ORIGINAL QUESTION:

Japanese speakers (and other non-English speakers) sometimes get confused about when to use the article "THE" a definite modifier (one example being "THE") in English versus the article "A" an indefinite modifier (one example being "A") in English. Likewise, English speakers sometimes get confused about when to use the particle は versus the particle が in Japanese.

An idea occurred to me recently which might be able to link the use of these English articles modifiers with the use of these Japanese particles. I'd like to explain this idea, and then I'd like feedback as to how valid this idea of mine might or might not be.

Suppose that you and I are having a conversation, and you ask me what I'm doing tomorrow. If I was speaking English, I might say, "A friend asked me to lunch tomorrow." But if I want to tell you this in Japanese, I believe that it would be ...

ともだち が [asked me to lunch tomorrow]

(I'm sorry, but my Japanese vocabulary knowledge is weak, but the translation of "asked me to lunch tomorrow" is not pertinent to what I'm asking about here, anyway).

Then, suppose you follow up by asking me, "Oh, what restaurant are you going to?"

I might respond as follows in English: "The friend likes to cook. We'll be eating at home." In Japanese, I believe that would be ...

ともだち は [likes to cook. We'll be eating at home]

(Again, the translation of "likes to cook. We'll be eating at home" is not pertinent to what I am asking about here.)

Notice that in my first sentence, the English is "A friend" (which uses an indefinite modifier), and we use が in Japanese. And in my second sentence, the English is "THE friend" (in which we use a definite modifier), and we use は in Japanese.

So, would it be safe to say that if we are correctly using an indefinite article modifier in English such as "A" or "SOME" or no modifier at all in the plural case (which implies indefinite) to describe the subject or topic of an English sentence, then we would tend to use が in Japanese? And would it also be safe to say that if we are correctly using a definite article modifier such as "THE" or "THESE" in English to describe the subject or topic of a sentence, then we would tend to use は in Japanese?

And conversely, would it be safe to say that when が is correctly used for the sentence subject in Japanese, an indefinite article modifier such as "A" or "SOME" or an empty implied modifier would generally be correct in English? And would it be safe to say that when は is correctly used for the sentence topic in Japanese, a definite article modifier such as "THE" or "THOSE" would generally be correct in English?

I know that this "rule" wouldn't work 100-percent of the time. However, it seems to me that it could work in at least many cases, and therefore, perhaps could it be a good mnemonic device for English speakers to help them decide when to use が and は? And likewise, perhaps could it be a good mnemonic device for Japanese speakers to help them decide when to use "A" and "THE" definite or indefinite modifiers in English?

What are your opinions about this idea of mine?

And again, based on the discussion below, I realize that this original proposal of mine is not as helpful as I was originally hoping, and I'm only leaving it here for reference.

Answer 1

As you pointed out, such a similarity does exist, and mentioning it on the first page of the relevant explanation in a Japanese textbook can work well as an icebreaker to draw the reader's interest. In fact, this answer is the most-voted answer on this site, and has a similar explanation. Without explaining it in this way, some learners might not even realize that distinguishing between は and が is important.

However, if understanding the difference between は and が were as simple as this, learners would not be so confused. In reality, the usage of a/the and は/が differ in most cases, and it would take several dozen pages of explanation just to give learners a rough understanding of how to use them. Basically, once you realize that these differences are important, it's faster to learn how to use them by forgetting their connections to the language you already know.

I have an English grammar book for Japanese high school students, and it has a chapter of several dozen pages solely on articles. Most of the content written there cannot be compared to the differences between は and が at all.

Answer 2

TL;DR There is no relationship between the usage of a/the to the usage of は/が. They belong to completely different categories and should not be compared. It's like comparing apples to oranges.

I'm not gonna explain the differences of は and が here as it's a lengthy description and one could easily find a LOT of resources online dedicated to to the usages of は and が, so I'm gonna stick to your question here.

First, let's note how は and が and a and the have different grammatical functions in their corresponding languages, and those do not line up.

a - the indefinite article to precede an unspecific item
the - the definite article to precede a specified item or commonly-known item (THE sun, THE moon, THE Pacific Ocean)

は - the particle marking the topic of the sentence, could be subject, could be object, could be any other info like time/place/etc.
が - marks strictly the subject of the sentence.

See how they do not line up at all? In your examples they do, but it is in no way indicative of a general pattern.

Second, English has not only a and the, but also article-less sentences. Consider the following sentence:

Cats eat fish.

If we change it to either a cat eats fish, or the cat eats fish, the meaning would not be the same. In Japanese, Cats eat fish should be

猫{ねこ}は魚{さかな}を食{た}べる

The は means we're discussing the topic cats in general, so in general, cats are a kind of animal that would eat fish. Now consider this:

Where is the fish ?! The cat ate it.
魚{さかな}はどこ？！　猫{ねこ}が食{た}べた。

Here, the が makes cats the subject, telling that it's the cat that performed the action of eating the fish. The English sentence uses the because it's a known cat to the speaker and listener, but in Japanese we use が because we are not discussing cats in general. This is contradictory to the statement that if we are correctly using a definite article such as "THE" in English to describe the subject or topic of a sentence, then we would tend to use は in Japanese. Note that Japanese doesn't have articles either.