はず, べき, わけ, つもり: Reasoning Grammar in Japanese

Core examples: 来るはず, するべき, わけがない, 行くつもり, そういうわけではない, 知っているはずだ.

Grammar for thinking, not just events

Some Japanese grammar does not describe what happened. It describes how the speaker is reasoning.

Consider:

田中さんは来るはずです。 Tanaka should come / is expected to come.

もっと早く連絡するべきです。 You should contact them earlier.

そんなわけがない。 That cannot be true.

来年、日本へ行くつもりです。 I intend to go to Japan next year.

These forms express expectation, obligation, explanation, denial, intention, and speaker stance.

The key principle is:

はず, べき, わけ, and つもり are reasoning grammar. They show how the speaker connects facts, norms, plans, and conclusions.

はず: expectation based on reason

はず expresses an expectation that should follow from evidence, plans, rules, or assumptions.

Examples:

田中さんはもう着いているはずです。 Tanaka should have arrived by now.

今日は休みのはずだ。 Today should be a holiday.

彼は知っているはずです。 He should know.

はず does not mean moral “should.” It means “given what I know, this is expected.” The basis may be schedule, prior information, rule, memory, promise, or ordinary logic.

If the expected result fails, はず often signals surprise:

来るはずだったのに、来なかった。 He was supposed to come, but he did not.

べき: obligation or normative judgment

べき expresses what should be done according to a norm, rule, responsibility, ethics, or speaker judgment.

Examples:

約束は守るべきです。 You should keep promises.

もっと早く相談するべきだった。 I should have consulted earlier.

この問題は社会全体で考えるべきだ。 Society as a whole should think about this issue.

べき can sound strong, judgmental, formal, or argumentative. It is not a soft suggestion by default. If you only mean “maybe it would be good,” softer forms such as したほうがいい or するといい may fit better.

わけ: reason, explanation, and logical conclusion

わけ relates to reason, meaning, or explanation. It appears in several important patterns.

だから遅れたわけですね。 So that is why you were late.

嫌いなわけではない。 It is not that I dislike it.

そんなわけがない。 There is no way that is true.

というわけで、今日は中止です。 For that reason, today is canceled.

わけ is discourse-heavy. It manages the logic between statements.

つもり: intention, plan, or self-understanding

つもり expresses intention or plan:

来年、日本へ行くつもりです。 I intend to go to Japan next year.

It can also express someone’s self-understanding or assumed stance:

彼は冗談のつもりだった。 He intended it as a joke.

自分では親切なつもりだった。 I thought I was being kind.

This second use is important. つもり can reveal mismatch between intention and effect.

助けたつもりだったが、迷惑だったらしい。 I thought I was helping, but apparently it was a nuisance.

はず vs つもり

Compare:

明日行くはずです。 He/she is expected to go tomorrow / should go.

明日行くつもりです。 I intend to go tomorrow.

はず is expectation based on reasoning. つもり is intention or plan, usually tied to the subject’s mind. If speaking about another person’s つもり, you need evidence or reporting:

田中さんは行くつもりらしい。 Apparently Tanaka intends to go.

べき vs はず

Compare:

彼は謝るはずです。 I expect him to apologize.

彼は謝るべきです。 He ought to apologize.

はず is expectation. べき is obligation. This distinction matters in arguments.

Example bank walkthrough

来るはず

Expected to come. Ask what evidence creates the expectation.

するべき

Should do as obligation. Watch for strong normative tone.

わけがない

Strong denial: “There is no way.”

行くつもり

Intend to go. Connects to plan or intention.

そういうわけではない

That is not what it means / It is not that. Denies a proposed explanation.

知っているはずだ

Should know, based on expectation. Not moral “should” unless context adds judgment.

Reasoning-grammar parse

When you meet these forms:

1. Identify the mental operation: expectation, obligation, explanation, or intention.
2. Find the basis: evidence, rule, plan, moral norm, explanation.
3. Check speaker confidence.
4. Check social force: advice, criticism, explanation, excuse, correction.
5. Translate stance, not just words.

Diagnostic contrasts: expectation, duty, explanation, plan

These forms become clearer when you contrast them around the same event.

Suppose the event is Tanaka coming to the meeting.

田中さんは来るはずです。 Tanaka is expected to come / should come, based on what I know.

The speaker has a basis: schedule, prior agreement, normal pattern, or evidence. If Tanaka does not come, the speaker’s expectation was wrong.

田中さんは来るべきです。 Tanaka should come.

This is normative. The speaker is judging what is appropriate, responsible, or required. It does not say Tanaka is likely to come.

田中さんが来ないわけがない。 There is no way Tanaka would not come.

This denies the logic of the opposite. It is not just expectation; it is a reasoning stance that rejects an explanation or possibility.

田中さんは来るつもりです。 Tanaka intends to come.

This describes intention, but be careful: with third persons, the speaker normally needs evidence, report, or context. For your own plans, つもり is direct. For another person’s plan, it may be reported or inferred.

A practical sorting table:

Learners should also watch negative combinations:

行くつもりはありません。 I do not intend to go.

行くはずがありません。 There is no expectation/possibility that he will go.

行くべきではありません。 One should not go.

These are different kinds of “not.” One denies intention, one denies expectation, and one denies appropriateness.

A strong tool for this article would place forms on a reasoning grid.

Suggested functions:

1. Category map: expectation, obligation, explanation, intention.
2. Contrast cards: はず vs べき, はず vs つもり.
3. Confidence scale: expected, impossible, intended, normative.
4. Argument mode: identify claim, basis, and conclusion.
5. Rewrite practice: soften べき into したほうがいい.
6. Context examples: workplace, advice, apology, plans, disagreement.

Final rule

はず, べき, わけ, and つもり are not just grammar points. They are tools for reasoning.

はず expects. べき judges. わけ explains. つもり intends.

Read the logic behind the sentence, and the translation will follow.