Japanese has several ways to say "you should do X," but the weight behind each expression varies greatly. Using the wrong one might make you sound preachy or dismissive. This article sorts out three common patterns for expressing advice and common sense.
Overview
| Expression | Weight | Core Meaning | Translation |
|---|---|---|---|
| ものだ | Universal truth | Human nature / common sense | That's just how it is |
| べきだ | Strong advice | Obligation / duty | You should... |
| ことだ | Light advice | Recommendation | You'd better... |
ものだ: That's Just How It Is
「ものだ」expresses universally accepted truths or natural human tendencies — not personal advice, but "everyone knows this":
| Example | Meaning |
|---|---|
| 地震の時は誰でも慌てるものだ。 | Everyone panics during earthquakes — it's human nature. |
| 年を取ると物忘れが多くなるものだ。 | You get forgetful as you age — that's just how it goes. |
| 人間は失敗するものだ。 | Humans make mistakes — it's only natural. |
Key: ものだ isn't telling someone "you should..." — it's stating a universal truth. The tone is "that's just how things are."
ものだ for Nostalgia and Exclamation
「ものだ」can also express nostalgia or amazement:
| Example | Meaning |
|---|---|
| 子どもの頃はよく川で遊んだものだ。 | I used to play by the river as a kid. (nostalgia) |
| よくここまで来られたものだ。 | I can't believe we made it this far. (amazement) |
べきだ: You Should Do This
「べきだ」expresses a strong sense of obligation or advice, like English "should/ought to":
| Example | Meaning |
|---|---|
| もっと早く彼に知らせるべきだった。 | I should have told him sooner. |
| 約束は守るべきだ。 | Promises should be kept. |
| 彼には恐れるべき力がある。 | He has power that should be feared. |
Caution: べきだ carries heavy weight. Using it toward elders or distant acquaintances can sound rude. It's more common in formal writing.
べきだ vs べきではない
| Positive | Negative |
|---|---|
| 行くべきだ。 (Should go) | 行くべきではない。 (Shouldn't go) |
| するべきだ / すべきだ (Should do) | するべきではない (Shouldn't do) |
「する」has two べき forms: するべきだ and すべきだ — the latter is more formal.
ことだ: Friendly Advice
「ことだ」offers lighter, friendlier advice, with the nuance of "if you want to achieve X, you'd better do Y":
| Example | Meaning |
|---|---|
| 資格を取りたいなら、もっと勉強することだ。 | If you want the qualification, you should study more. |
| 健康でいたいなら、毎日運動することだ。 | If you want to stay healthy, exercise every day. |
Key: ことだ typically appears in "if you want X, then do Y" contexts — gentle, well-meaning advice.
Three-Way Comparison
| Scenario | ものだ | べきだ | ことだ |
|---|---|---|---|
| Panicking in an earthquake | ✅ Human nature | ❌ Inappropriate | ❌ Inappropriate |
| Keeping promises | △ Too weak | ✅ Strong obligation | △ Too light |
| Suggesting exercise | ❌ Not universal truth | △ Too forceful | ✅ Gentle advice |
A helpful metaphor:
- ものだ = Laws of nature (the earth is round)
- べきだ = Legal obligations (you must obey)
- ことだ = A friend's suggestion (give it a try)
Summary
- ものだ = human nature / natural law (objective, not aimed at individuals)
- べきだ = obligation / strong advice (heavy tone, better for formal contexts)
- ことだ = gentle recommendation (light tone, good for everyday advice)
- ものだ can also express nostalgia and amazement
- Be careful using べきだ with superiors
Practice
1. Choose the right expression:
年を取ると、体力が落ちる____。
Show answer
年を取ると、体力が落ちるものだ。 This is a natural law (human nature), so use ものだ.
2. What's the difference between「約束は守るべきだ」and「約束は守ることだ」?
Show answer
- 守るべきだ: Strong tone — "Promises should be kept" (like a moral duty)
- 守ることだ: Light tone — "It's best to keep promises" (like friendly advice)
- In this context, べきだ is more natural since keeping promises is a moral obligation.
3. Which sentence sounds unnatural? Why?
- a. 地震の時は慌てるものだ。
- b. 地震の時は慌てるべきだ。
Show answer
b sounds unnatural. べきだ means "you should do X," but "you should panic" doesn't make logical sense — panicking is an involuntary reaction, not something you should or shouldn't do. Use ものだ to express "it's human nature."