Consider this sentence:

それは三十年前のことだから、もう[fill in the blank]。

The answer given by the workbook is 忘れた.

Choices are:

  1. 忘れる (forget)
  2. 忘れた (forgot)
  3. 忘れている (continued state of forgetting)
  4. 忘れていた (had forgotten, currently may or may not be forgotten)

My thought process:

Choice 1 is ruled out because it is present/future tense, but the question describes something in the past.

Choice 3 cannot make sense to me. If one is able to talk about something that one forgets, the person is currently not forgetting it. (I do not see how this can make sense in the first person) (Unless it's a dynamic state of memory where the person keeps forgetting and recalling bits and pieces?)

Choice 4 was my choice. I don't understand why 2 is correct while 4 is not. I thought 4 to be correct because he had forgotten about the issue, but is currently remembering it while making the statement.

(Question) Why is choice 2 correct and 4 wrong? And under what circumstances do we use 3 ?

  • “I thought 4 to be correct because he had forgotten about the issue, but is currently remembering it while making the statement.” I completely agree. I would not pass the test. Nov 5, 2011 at 17:15
  • It seems like 2 is the only one that makes sense without additional context.
    – istrasci
    Nov 5, 2011 at 18:57
  • 1
    @istrasci: No. If anyone says それは三十年前のことだから、もう忘れていた, the context is clearly understandable from this sentence alone. Nov 5, 2011 at 20:36
  • Hmm... the speaker does not necessarily have to remember the subject itself to remember learning about it. Think of forgetting a skill or academic subject, rather than forgetting a piece of information.
    – jkerian
    Nov 5, 2011 at 21:52
  • @Tsuyoshi, yes except the usage of もう in that sentence doesn't really make sense without further context. Saying you "had already forgotten" requires another time reference, otherwise it doesn't make sense. I mean it's obvious when you translate to english: "It happened 30 years ago, so I had already forgotten". This only makes sense in a context where they are talking about a time between 30 years ago and the present. The speaker must specify the time at which they had forgotten.
    – Muhd
    Nov 7, 2011 at 8:40

1 Answer 1


I am pretty sure that wherever you had this question, there was a context because any of these four can be correct depending on the context. If it was asked without context, I will have to say that your source is not reliable for studying Japanese.

  1. 僕はこれまで彼をある出来事のために恨んできた。でも、それは三十年前のことだから、もう忘れる。

  2. 僕はかつて難しい計算ができた。でも、それは三十年前のことだから、もう忘れた。

  3. 僕は難しい計算ができたはずだ。でも、それは三十年前のことだから、もう忘れている。今、試験を受けてみて分かった。

  4. そういえば、僕は以前にここに来たことがあった。でも、それは三十年前のことだから、もう忘れていた。

忘れる's inner event is done at an instance. So the use of ている form for this verb means that the completed state sustains. Together with tense, it can mean four things:

  • 1). Non-past non-perfective: 'the instantanious event of forgetting happens in non-past'
  • 2). Past non-perfective: 'the instantanious event of forgetting happened in past'
  • 3). Non-past perfective: 'the state of having forgotten has sustained up till now'
  • 4). Past perfective: 'the state of having forgotten has sustained up till past'
  • Actually there was just a single sentence. So I guess it's not very reliable then.
    – Flaw
    Nov 5, 2011 at 18:12
  • It would be good if your answer included explanations of why those forms are appropriate in their respective examples.
    – Flaw
    Nov 6, 2011 at 1:58
  • I am fairly certain that 忘れた is the best answer here, just from my intuition from hearing lots of japanese. I think you would be right if we were talking about a different verb, but 忘れる's conjugations take different meanings then what is normal since it is never an instantaneous event. So, as I say in my answer, 2 takes the meaning of 3 and 3 should not be used.
    – Muhd
    Nov 7, 2011 at 8:27

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