At last. The final でしょう.

It's been a long road, yeah?

But we made it.

We've already looked at all of the following uses of でしょう, except for the very last one:

1. Classic でしょう (Lesson #85)
　a. Seeking Agreement (ii.)
　b. Seeking Verification (i.)
　c. Expressing Sympathy (i.)
(Also, a detour to look at male and female language in Lesson #86)

2. Inward でしょう (iii.) (Lesson #87)
(Also, a detour to look at the very similar usage of ことか in Lesson #88)

3. でしょう of Conjecture (iv.)
　a. Weather でしょう (Lesson #89)
　b. General Conjecture　

So let's get this over with!

The "でしょう of Conjecture"

In addition to the weather-related uses that we saw yesterday, this meaning of だろう and でしょう is also used for talking about conjecture in general.

This could be a guess about the future, like this:

コウイチは今日のパーティーに来ないだろう。
コウイチ　は　きょう　の　パーティー　に　こない　だろう。
I doubt Koichi will come to the party tonight.
Literally: “コウイチ + は + today + の + party + に + won’t come + だろう.”

Or it can be used to speculate about things in the present, like this:

ケンは今ごろタイに着いているでしょう。
ケン　は　いまごろ　タイ　に　ついている　でしょう。
Ken is probably arriving in Thailand right about now.
Literally: "Ken + は + around now + Thailand + に + is arriving + でしょう."

Or it can be used to speculate about things in the past, like this:

たくさん勉強したのだろう。
たくさん　べんきょう　した　の　だろう。
She must have studied a lot.
Literally: "a lot + studied + ん + だろう."
Note: This の shows that this phrase is an explanation for something. For example, maybe "she" got a perfect score on her test, and now I'm thinking that it's because she studied a lot.

That's not too hard, right?

Wrong.

Preparing for this lesson was a nightmare, because...

People don't really use this でしょう？

I went through my grammar books, studying the "でしょう of Conjecture."

I gathered the handful of example sentences shown above.

Then, as I was writing my first draft of this lesson, I started asking Rei lots of questions about the nuances of the language, when she dropped this bomb on me:

In conversations, people don't really use the でしょう／だろう shown above.

What?!

Aside from the fact that I've been using this "でしょう of Conjecture" for years, it also shows up as a JLPT N4 grammar point. And the N5 and N4 stuff tends to be at least somewhat useful in everyday life (although it's usually too stiff and/or formal).

So yeah--I didn't see what the problem was.

After a lot of back and forth, though, I realized that--contrary to my new-found fears--I have been using this grammar correctly for some time now.

Allow me to explain.

As with most textbook grammar topics, the problem lies in stiffness and formality.

You are very unlikely to hear someone say:

コウイチは今日のパーティーに来ないだろう。
コウイチ　は　きょう　の　パーティー　に　こない　だろう。
I doubt Koichi will come to the party today.
Literally: “コウイチ + は + today + の + party + に + won’t come + だろう.”

But! You are fairly likely to hear someone say:

コウイチは今日のパーティーに来ないだろうな。
コウイチ　は　きょう　の　パーティー　に　こない　だろう　な。
I doubt Koichi will come to the party today.
Literally: “コウイチ + は + today + の + party + に + won’t come + だろう + な.”

Just that one little particle changes it that much?

Indeed, my friend.

That because な is kind of like "Inward ね." It's like you're saying "huh?" or "right?" to yourself.

So it's very common when you're are speculating about something.

That all makes sense to me. I get why using な makes sense here. What I don't get is why the sentence sounds so strange without it.

I want to explain this... but I can't think of any explanation that will be clear, concise, and easy to digest.

All I know is that the example without the な above sounds mega-stiff and formal... which means that people pretty much never say it out loud.

Imagine someone said this:

A:
ミホが百点取ったって。
ミホ　が　ひゃくてん　とった　って。
Miho said she got 100(%) on the test.
Literally: "Miho + が + 100 points + took + って."

I want to respond with, "She must have studied a lot."

The following sentence, however, is too formal:

B:
たくさん勉強したのだろう。
たくさん　べんきょう　した　の　だろう。
She must have studied a lot.
Literally: "a lot + studied + ん + だろう."

To make it more conversational, we should:
(1) change the の to ん, and
(2) add a な to the end of it.

Like this:

B:
たくさん勉強したんだろうな。
たくさん　べんきょう　した　ん　だろう　な。
She must have studied a lot.
Literally: "a lot + studied + ん + だろう + な."

For an added boost of casual flavor, we could also change たくさん to めっちゃ：

B:
めっちゃ勉強したんだろうな。
めっちゃ　べんきょう　した　ん　だろう　な。
She must have studied a lot.
Literally: "way/super/very + studied + ん + だろう + な."

Please note that, since these examples are using な, the listener does not need to respond.

If we wanted them to respond, then we could change the な to ね, like this:

B:
めっちゃ勉強したんだろうね。
めっちゃ　べんきょう　した　ん　だろう　ね。
She must have studied a lot.
Literally: "way/super/very + studied + ん + だろう + ね."

Realistically speaking, the use of だろうね probably deserves its very own lesson, as it's such a common sentence-ending in Japanese. But I think we've all had enough of でしょう／だろう, so that's not happening. This ends today!

だろうね seems to get translated to "I suppose" and "I guess," a lot... although I think the best translation will always differ based on context. Let's just not worry about it!

Here's how we could use だろうね in (a casual version of) a sentence we saw a little earlier:

ケンは今ごろタイに着いてるだろうね。
ケン　は　いまごろ　タイ　に　ついてる　だろう　ね。
Ken's probably arriving in Thailand right about now.
Literally: "Ken + は + about now + Thailand + に + is arriving + だろうね."
Note: Since this is a more casual sentence, we removed the い from 着いている.

Confusing stuff, man.

Oh, and we're not finished yet!

You can't "predict" your own action with でしょう／だろう.

Sentences like this don't fly:
✖　私は明日出かけるでしょう。
✖　わたし　は　あした　でかける　でしょう。
✖　I will probably go out tomorrow.

This makes you sound like you're a fortune-teller reading your own palm, or something.

Rather, you'd say:

〇　私は明日出かけます。
〇　わたし　は　あした　でかけます。
〇　I will go out tomorrow.
Literally: "I + は + tomorrow + go out."

Or you could say:

〇　私は明日出かけるつもりです。
〇　わたし　は　あした　でかける　つもり　です。
〇　I'm planning to go out tomorrow.
Literally: "I + は + tomorrow + go out + つもりです."

Note: Using "Dictionary-form VERB + つもり（です）" is a useful formula for "I intend to VERB" and "I'm planning to VERB" constructions.

I used formal sentences for both of those, because the "でしょう of Conjecture" without な or ね is rather stiff and formal. However, we could also make casual sentences like these:

明日出かけるつもり。
あした　でかける　つもり。
I'm planning to go out tomorrow.
Literally: "tomorrow + go out + つもり."

明日出かける。
あした　でかける。
I'm going out tomorrow.
Literally: "tomorrow + go out."

Ah, I love you, casual Japanese.

You're so simple and straightforward.

Are we finished, でしょうか？

These でしょう lessons just never end!

There's one last piece to the puzzle, though.

It's quite common to hear でしょうか (and NOT だろうか) in formal questions in Japanese.

Many of you will already know that we use ですか at the end of formal questions, such as saying:

どこですか。
Where is it?
Literally: "where + ですか."

Instead of ですか, we can also use でしょうか, and the result is a question with a softer, less-direct nuance:

どこでしょうか。
Where might it be? // I was wondering where it is. // Where is it?
Literally: "where + でしょうか."

I was a little bit surprised to see that one of my grammar books lumps this でしょうか among all of the other "でしょう of Conjecture," including both the "Weather でしょう" and the でしょう we saw above.

The more I think about it, though, it does make sense, because the nuance is that I am or have been thinking/wondering about the answer to the question that I'm asking.

It's almost like I'm asking a question to myself, out loud, and hoping for an answer... which explains why it's a soft, indirect question form.

Note that all of the following are quite formal...

どうしてでしょうか。
Why is that?
Literally: "why + でしょうか."

本当なのでしょうか。
ほんとう　なの　でしょうか。
Is that really true?
Literally: "true + なの + でしょうか."

一緒にどうでしょうか。
いっしょに　どう　でしょうか。
Would you like to go together?
Literally: "together + how + でしょうか."

Although my book categorizes them together, I have a hard time imagining that the following are "Soft ですか" questions. They sound more like internal monologues to me...

大学に受かるでしょうか。
だいがく　に　うかる　でしょうか
I wonder if I'll [he'll] get accepted (to the university). // Will I [he] get into the university?
Literally: "university + に + be accepted + でしょうか."

時間通りに到着できるでしょうか。
じかん　どおり　に　とうちゃく　できる　でしょう　か。
Do you suppose we'll be able to arrive on time? // I wonder if we'll be be able to arrive on time.
Literally: “on time + arrive + can + でしょうか.”

How can we possibly remember which でしょう is which?!

Honestly, yo, I have no idea.

Writing these lessons, I was always getting mixed up about which specific usage of でしょう／だろう I was talking about, because they're pretty similar.

While I do think it's useful to know the differences in usage and meaning, I wouldn't stress about it too much. I was using でしょう pretty inaccurately (also, avoiding using it because I was confused) for years. But, in time, I got a sense for the language, and different uses just started making sense naturally.

I think this comes down to the necessity for extremely high volumes of relevant, level-appropriate language exposure.

In time, you'll be able to recall/recite several times that you've heard certain grammatical constructions being used, and those become the basis for your understanding of grammar... rather than just some rule you read in a grammar book.

That takes time, though... so we can get a head start with all of this lesson madness.

Good luck in your studies!