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文法
Modality B2

Perfect modals

Judge past situations with modal + have + past participle for deduction, possibility, regret, and criticism.

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図解ガイド

Perfect modals: a present judgement about the past

NOW: your judgement
        │
        ▼
[modal] + have + [past participle]
        │
        └──────────────► PAST event/result

Choose the modal for your attitude now:

SURE guess       She must have been exhausted after the flight.
POSSIBLE guess   I might have left it at the office.
REGRET/criticism You should have told us earlier.
UNNECESSARY      We needn’t have bought more bread.

Mental check:
not “modal + past tense”
✓ modal + have + past participle

Use modal + have + past participle when you are speaking now about how you see a finished past situation.

Introduction

What perfect modals do

Perfect modals judge the past from the present. The form is modal + have + past participle. You are not simply reporting a past event; you are adding an attitude: strong deduction, possibility, regret, missed opportunity, or criticism. In “She must have been exhausted after the flight,” the speaker looks at evidence and makes a strong conclusion. In “I might have left it at the office,” the speaker offers one possible explanation. The past situation is fixed; the modal shows how the speaker thinks about it now.
Core 文法：B2 語彙：B1 Neutral

She must have been exhausted after the flight.

Use must have + past participle when the evidence makes a past conclusion very likely.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

must have been
modal judgment about a past state
Strong deduction about the past: the speaker is almost sure.
ひとまとまりで覚える
exhausted after the flight
past situation
The state being judged.
Core 文法：B2 語彙：A2 Neutral

I might have left it at the office.

Might have + past participle presents one possible explanation for a past situation.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

might have left
modal judgment about a past action
A possible past action; the speaker is not sure.
ひとまとまりで覚える
it at the office
time reference
The possible place of the forgotten item.
Core logic

The basic meanings

Think of perfect modals as a spotlight aimed backward. The event is behind you, but your present mind judges it. Use must have for a strong positive conclusion: “The lights are off; they must have gone home.” Use can’t have or couldn’t have for a strong negative conclusion: “He can’t have seen my message yet.” Use may have, might have, or could have for possibility. Use should have for the right action that did not happen: “You should have told us earlier.” Use shouldn’t have for a wrong action that did happen. Use needn’t have when something happened but was unnecessary: “We needn’t have bought more bread.”
Negative 文法：B2 語彙：A2 Neutral

He can’t have seen my message yet.

Can’t have + past participle rejects a past conclusion, often because the evidence points the other way.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

can’t have seen
modal judgment about past impossibility
Strong negative deduction about the past: the speaker believes it was impossible or not true.
ひとまとまりで覚える
my message yet
object of perception
The thing judged as not seen.
Core 文法：B2 語彙：A2 Neutral

You should have told us earlier.

Should have + past participle says a better action was expected in the past.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

should have told
modal criticism about the past
Says the right action was not done; often expresses criticism or regret.
ひとまとまりで覚える
us earlier
person affected
Who should have received the information and when.
Core 文法：B2 語彙：A2 Neutral

We needn’t have bought more bread.

Needn’t have + past participle means someone did something, but there was no need.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

needn’t have bought
modal regret about unnecessary action
The action happened, but it was unnecessary.
ひとまとまりで覚える
more bread
thing bought
The unnecessary item.
Core pattern

The form

The core pattern is fixed: subject + modal + have + past participle. The modal does not take -s, and have does not change to has or had. The past participle carries the main lexical meaning: gone, seen, told, forgotten, been, done. For questions, move the modal before the subject: “Could you have sent it to the wrong address?” For negatives, add not after the modal: “They couldn’t have known.” Common contracted forms are must’ve, might’ve, could’ve, should’ve, shouldn’t have, and couldn’t have. In careful writing, the full form is often clearer.
Formal 文法：B2 語彙：B1 Formal

The client may have misunderstood the instructions.

May have is a little more formal or careful than might have in many contexts.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

may have misunderstood
modal frame
A polite or cautious possibility about a past action.
ひとまとまりで覚える
the instructions
object
What may have been misunderstood.
Question 文法：B2 語彙：A2 Neutral

Could you have sent it to the wrong address?

Questions put the modal before the subject: Could you have sent...?

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

Could you have sent
question frame
Asks whether a past action was possible or happened.
ひとまとまりで覚える
it to the wrong address
object and recipient
The possible mistaken action.
Sentence xray

Sentence X-ray

In “You could have called me first,” each part has a job. “You” names the person being judged. “Could” gives the modal meaning: possible, and often mildly critical here. “Have called” places that possible action before now. “Me first” gives the expected action and timing. Compare “They couldn’t have known about the delay.” The negative modal blocks the past possibility: knowing was not realistically possible. The structure is small, but the meaning is rich: one sentence can show evidence, expectation, blame, regret, or sympathy depending on the modal and context.
Spoken 文法：B2 語彙：A1 Informal

You could have called me first.

Could have often sounds like a mild criticism when the missed action would have helped.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

could have called
modal frame
An action was possible in the past, but it did not happen or is only imagined.
ひとまとまりで覚える
me first
time phrase
The expected timing or order.
Negative 文法：B2 語彙：A2 Neutral

They couldn’t have known about the delay.

Couldn’t have can mean past impossibility, close to can’t have but often slightly softer or more contextual.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

couldn’t have known
strong negative deduction
The speaker believes knowing was impossible in that past situation.
ひとまとまりで覚える
about the delay
content clause
What could not have been known.
Usage rules

Choosing the right modal

Choose the modal by the job you need. For deduction from evidence, use must have or can’t have. For uncertain possibilities, use may have, might have, or could have. May have can sound a little more formal or cautious than might have. For regret and criticism, use should have or shouldn’t have. For imagined past results, especially with if, use would have: “I would have helped if you had asked.” For missed opportunities or possible outcomes, use could have: “It could have been much worse.” Perfect modals usually judge one completed past situation, not a repeated habit.
Negative 文法：B2 語彙：B1 Neutral

You shouldn’t have opened that attachment.

Shouldn’t have + past participle criticizes something that did happen.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

shouldn’t have opened
negative advice about the past
Says a past action was wrong or unwise.
ひとまとまりで覚える
that attachment
object
The action being criticized.
Core 文法：B2 語彙：A2 Neutral

I would have helped if you had asked.

Would have is common in third conditional meanings: the helping did not happen because the condition did not happen.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

would have helped
unreal past ability or opportunity
Shows what someone was willing or likely to do in an unreal past condition.
ひとまとまりで覚える
if you had asked
condition
The condition that did not happen.
Contrast

Perfect modals vs past obligation or expectation

The closest common confusion is between perfect modals and past arrangements or expectations. “The package was supposed to arrive before lunch” means there was a plan or expectation. It does not say what the speaker now concludes from evidence. “The package must have arrived while we were out” is a deduction based on evidence, such as a delivery notice. Also compare “had to.” “She had to leave early” says there was a real past obligation. “She must have left early” is a conclusion about what probably happened.
Contrast 文法：B2 語彙：A2 Neutral

The package was supposed to arrive before lunch.

Was supposed to describes an arrangement or expectation, not a deduction like must have arrived.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

was supposed to arrive
unfulfilled expectation
A past arrangement or expectation, not a judgment made from evidence.
ひとまとまりで覚える
before lunch
time phrase
When the arrival was expected.
Contrast 文法：B2 語彙：A2 Neutral

The package must have arrived while we were out.

Must have arrived judges what probably happened, unlike was supposed to arrive, which reports a plan.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

must have arrived
past deduction
A strong conclusion about the past based on evidence.
ひとまとまりで覚える
while we were out
evidence link
The time inferred from the evidence.
Danger zone

Common mistakes

Two form mistakes are very common. First, do not change have after the modal. Say “She must have forgotten the meeting,” not “She must has forgotten the meeting.” The modal already controls the verb form. Second, do not add to after ordinary modals. Say “You should have checked the file,” not “You should have to checked the file.” Be careful with pronunciation too: should’ve can sound like should of, but the grammar is always should have. In writing, “should of,” “could of,” and “would of” are incorrect.
Mistake 文法：B2 語彙：A2 Neutral

She must has forgotten the meeting.

After a modal, use have + past participle, not has + past participle.

Corrected 文法：B2 語彙：A2 Neutral

She must have forgotten the meeting.

The modal does not change for he, she, or it: she must have, not she must has.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

must have forgotten
correct perfect modal form
Modal + have + past participle is the fixed frame.
ひとまとまりで覚える
the meeting
object
What was probably forgotten.
Mistake 文法：B2 語彙：A2 Neutral

You should have to checked the file.

Do not use to after most modals in perfect modal structures.

Corrected 文法：B2 語彙：A2 Neutral

You should have checked the file.

Use modal + have + past participle: should have checked.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

should have checked
correct criticism frame
Says the checking was the right past action, but it was not done.
ひとまとまりで覚える
the file
object
What should have been checked.
Summary

What to remember

Perfect modals are useful because they combine time and attitude in one compact frame. Use modal + have + past participle to look back and judge: “must have” for strong positive deduction, “can’t have” or “couldn’t have” for strong negative deduction, “may/might/could have” for possibility, “should have” for regret or criticism, “shouldn’t have” for wrong past action, “needn’t have” for unnecessary action, and “would have” for unreal past results. Always keep the form stable: no -s on the modal, no “has” after it, and no “to” before the participle.
Spoken 文法：B2 語彙：A2 Neutral

It could have been much worse.

Could have been often evaluates how a past situation might have turned out differently.

意味のかたまり

単語ごとではなく、意味のかたまりで文を読んでみましょう。

could have been
missed opportunity
Shows a possible past result that did not become real.
ひとまとまりで覚える
much worse
result phrase
The imagined possible result.
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