In the sample sentences for the lesson “る-Verb (Negative)” the following two sentences are given as examples:
は、肉を食べない。
(I don’t eat meat)
and
私は黒板が見えません。
(I can’t see the blackboard).
To me they both seem to be sentences of the same form, so why does one use を and the other が?
The English translations are equivalent in meaning but not grammatically. Japanese sometimes phrases things using different grammar than we may use in English.
食べる is a transitive verb so takes a direct object, marked with を; the subject is marked with が. 見える is an intransitive verb and thus has no direct object, just a subject that is marked with が.
I’ve used some jargon just then so let me know if that doesn’t make sense or you have another question!
Ok, that makes it a bit clearer.
If the subject for 食べる is marked with が, then why isn’t it
私が、肉を食べない。As I am the subject (the one who does not eat meat)?
Or would it only use が if there was a specific meat? “I don’t eat that meat?” (私はこれが肉を食べない。）
I think your understanding is backwards. The particle is highlighting the word that comes before it. So in your example sentence above, it’s not that meat being emphasized, but kore.
My understanding for these types of sentences (where it feels like both が/は would work), is that が will be able to specifically respond to the question being asked.
For example, let’s say a set of meals has just arrived and one of them is vegetarian. Someone might ask who it is that doesn’t eat meat. In that case, you could respond using the が particle because you’re emphasizing that it is you that doesn’t eat meat out of the group of people (私が = I am the one… (that doesn’t eat meat)).
I am also a beginner, but this is how I’ve been able to make sense of the particles. I hope this helps you a bit.
この肉 would be used if you were talking about a speficic meat in front of you, not これが肉. The verb would still apply to the acting party (subject), not the meat itself. The noun marked by は is not always the acting party, but it can be. If が isnt’ being stated directly, then there should be some context within the sentenece that can point you to the acting party.
Your second sentence would work if the person was pointing at their mouth and using これ to refer to it, and が would be marking it as the thing that is doing the eating. That woulｄ proably come off either joking or pretentious, depending on the context; “This (my mouth) doesn’t eat meat.”