How sure you are

Japanese has seven or eight ways of not quite asserting something, and every textbook lays them out as a ladder of probability, which is the wrong picture and makes them impossible to choose between. They are not degrees of doubt. They are kinds of evidence, and once you sort them that way the choices mostly make themselves.

Not degrees of doubt but kinds of evidence

Ask, of any hedged claim, where it came from. Japanese has a form for each answer.

I worked it out from something I know: はず. I am as good as certain: にちがいない. It is my guess, with nothing much behind it: でしょう or だろう. It is one possibility among others: かもしれない. I can see signs of it: ようだ or みたい. Somebody told me, or I picked it up somewhere: らしい. I was told this specifically and am passing it on: そうだ. It looks that way from here: the other そう.

Two of those pairs are close enough to blur, and the last two are one kana apart in writing and completely different in meaning. Everything else in this lesson is a consequence of the list above.

The reason the probability picture fails is easy to demonstrate. 田中たなかさんは来くるはずです and 田中たなかさんはたぶん来くるでしょう can both be said about a situation where you would put the odds at the same place. What differs is that the first commits you to having a reason, and invites the question "why do you think so?", to which you must have an answer. The second commits you to nothing. That is a difference of grounds, not of percentage, and attaching numbers to these forms is the single most common way of learning them wrong.

はず and にちがいない: expectation with a reason behind it

はず means that something follows from what you know. It is a noun, so it attaches like one: plain verb or い adjective directly, な adjective with な, and a noun with の.

今日きょうは日曜日にちようびだから、銀行ぎんこうは休やすみのはずです kyou wa nichiyoubi da kara, ginkou wa yasumi no hazu desu today is Sunday, so the bank should be closed

電気でんきがついているから、誰だれかいるはずだ denki ga tsuite iru kara, dareka iru hazu da the light is on, so somebody must be in

Notice that both sentences supply their reason explicitly with から. That is not decoration. A はず sentence with no visible reason invites one, and a speaker who cannot give one has used the wrong form.

Two derived shapes are worth having. はずがない says the opposite: there is no way this could be so. そんなことがあるはずがない, "that can't possibly be right". And はずだった says that something was supposed to happen and did not: 三時さんじに来くるはずだったのに、来こなかった. The のに of the previous lesson but two is doing its usual work there, carrying the speaker's irritation.

にちがいない is stronger and more emphatic, closer to English "must have". It attaches to the plain form, with nouns taking nothing at all: 田中たなかさんは知しっていたにちがいない, "Tanaka must have known". It belongs to writing and to dramatic speech; in ordinary conversation はず covers most of the same ground with less weight.

Example. Your flatmate's shoes are by the door. Say they must be in, and then say the same thing without committing to a reason.

With a reason: 靴くつがあるから、家いえにいるはずです. With none: たぶん家いえにいるでしょう. The first sentence would be strange without the から clause, or at least would immediately prompt どうして, because はず announces that a chain of reasoning exists. The second makes no such promise and cannot be challenged the same way. This is the whole difference between the two forms, and it is a difference in what you are undertaking to defend rather than in how likely you think it is.

Now you. The train was due at three and has not arrived. Say that it was supposed to come at three, and then say that this cannot be right.

でしょう and かもしれない: the guess

でしょう, plain form だろう, is the ordinary word for probability. It attaches to the plain form and nouns take nothing: 明日あしたは雨あめでしょう. It pairs naturally with たぶん.

たぶん明日あしたは雨あめでしょう tabun ashita wa ame deshou it will probably rain tomorrow

でしょう has a second life that has nothing to do with probability. Said with a rising intonation it seeks agreement, in the way an English tag question does: 面白おもしろかったでしょう, "it was good, wasn't it?". Whether a given でしょう is a guess or an appeal is decided by the intonation and by whether the listener could possibly know, which is one of the places where reading Japanese loses information that speech carries.

かもしれない, polite かもしれません, is weaker: this is one possibility. 明日あしたは雨あめかもしれません says rain is on the cards, not that it is likely. Attachment is the same, with nouns taking nothing before it. In casual speech it contracts all the way down to かも, which is a complete and very common answer on its own.

ようだ and みたい: what the signs suggest

ようだ says that the speaker has inferred something from evidence they have taken in directly.

道みちがぬれているから、雨あめが降ふったようだ michi ga nurete iru kara, ame ga futta you da the road is wet, so it seems it rained

Attachment follows the noun pattern, because よう is a noun: plain verbs and い adjectives directly, な adjectives with な, and nouns with の. So 病気びょうきのようだ, 元気げんきなようだ.

みたい is the conversational equivalent and means the same thing. Its attachment is easier, since nouns take nothing: 病気びょうきみたいだ, 風邪かぜをひいたみたいです. If you remember one difference between them, remember that の before ようだ becomes nothing before みたい.

Both also do simile, which is worth knowing so that you do not misread it as inference: 氷こおりのように冷つめたい, as cold as ice; 夢ゆめみたいだ, it's like a dream.

らしい: what you picked up

らしい is inference too, but from outside information rather than from what is in front of you. Somebody said so, you read it somewhere, it is going around.

田中たなかさんは来週らいしゅう引ひっ越こすらしい Tanaka-san wa raishuu hikkosu rashii apparently Tanaka is moving next week

It attaches to the plain form and nouns take nothing: 彼かれは医者いしゃらしい. The distance it puts between the speaker and the claim is the point: らしい is what you use when you would rather not be held responsible for the information.

There is a second らしい, attached straight to a noun, that means "typical of" rather than "apparently": 男おとこらしい, manly; 子こどもらしい, childlike. 今日きょうは春はるらしい天気てんきです means the weather is properly spring-like, not that it is rumoured to be spring. Context separates them, and the "typical" sense always sits before a noun or at the end with a noun immediately in front.

The two そう, one kana apart

This is the pair that has to be got exactly right, because the two forms differ by a single kana and mean unrelated things.

Hearsay そうだ attaches to the plain form, complete and unaltered, and means "I hear that".

天気予報てんきよほうによると、明日あした雨あめが降ふるそうです tenki yohou ni yoru to, ashita ame ga furu sou desu according to the forecast, it's going to rain tomorrow

Appearance そう attaches to the stem, the part left when ます or the final い comes off, and means "it looks like".

雨あめが降ふりそうです ame ga furisou desu it looks like rain

降ふるそうです and 降ふりそうです. One kana. The first is a report of what the forecast said; the second is you looking at the sky. Nouns make the difference visible in another way: hearsay takes だ, giving 雨あめだそうだ, while appearance cannot attach to a plain noun at all, so there is no 雨あめそうだ.

Appearance そう has some mechanics of its own. い adjectives drop their い: おいしそうですね, said over a plate of food, is one of the most useful sentences in Japanese. な adjectives attach directly: 元気げんきそうですね. Two forms are irregular and both are common: いい gives よさそう, and ない gives なさそう, as in 時間じかんがなさそうだ. And appearance そう never attaches to a past form, which is a useful negative test: 降ふったそう can only be hearsay.

There is also a semantic restriction. Appearance そう describes what something looks like it will be or might be, from surface signs, so it does not apply to properties you can simply see. Of a cake you have not tasted, おいしそう is right. Of a person plainly in front of you, きれいそう is wrong, because prettiness is not inferred from signs; you just say きれいです.

Example. You are looking out of the window at heavy black cloud. Then you check your phone, which says the forecast is for rain. Give the two sentences.

Looking at the cloud: 雨あめが降ふりそうです, from the stem 降ふり, because you are inferring from what you can see. Reading the forecast: 明日あした雨あめが降ふるそうです, from the plain form 降ふる, because you are relaying what a source told you. Swapping them produces two wrong sentences rather than one clumsy one: 降ふるそうです while staring at a cloud claims a source you do not have, and 降ふりそうです about the forecast claims the forecast merely looks like rain.

Now you. Give the appearance form of おいしい, いい, ない and 元気げんき, and the hearsay form of 高たかい and 学生がくせいだ.

Choosing, and where the boundaries blur

Example. Your colleague has not been at work for three days. Say it with ようだ, with らしい and with そうだ, and say what changes.

田中たなかさんは病気びょうきのようです says you have worked it out from what you can see: the empty desk, the cancelled meetings. 田中たなかさんは病気びょうきらしいです says you heard it from someone, and quietly declines responsibility for it. 田中たなかさんは病気びょうきだそうです says you were told, and are passing on the report as given, usually with the source available if asked. Note the three different attachments after a noun: の for ようだ, nothing for らしい, だ for hearsay そうだ.

Now you. You ring a shop at 8pm and nobody answers. Its posted hours are 9 to 6. Which form fits, and which two do not?

Now the honest part. ようだ and らしい overlap substantially, and plenty of sentences accept either with only a shading of difference in whether the speaker is claiming to have worked it out or to have been told. でしょう and かもしれない are separated by degree rather than by kind, and speakers differ in where they put the line. What does not blur is the pair of そう, the attachment rules, and the requirement that はず come with a reason. Get those three right and the rest is fine-tuning that listening will do for you.

Vocabulary

Everything up to here has been about the shape of a clause. The rest of the course is about the shape of the verb, and about the social information Japanese packs into it. Before that, though, one lesson away from grammar entirely: your sentences are now complex enough to read real Japanese with, and the thing standing in the way is no longer the grammar but the writing system.