Learn Hardcore Japanese: dare demo ziyuu ni iken wo ieru syakai ha taisetu da to omoimasu. - I think a society where anyone can freely express their opinions is important.

誰でも + positive verb → “anyone can … / everyone …”
- 誰でも　自由に　意見を言える
  “Anyone can freely express their opinion.”
誰も + negative verb → “no one …”
- 誰も　自由に　意見を言えない
  “No one can freely express their opinion.”

So:

誰でも = “anyone/everyone” (used with positive verbs)
誰も = “no one” (when followed by a negative verb)

Using 誰も in the original sentence without changing 言える to 言えない would be ungrammatical.

Why is 自由 followed by に? What does 自由に mean?

自由 is a na‑adjective meaning “free.”

Na‑adjectives become adverbs by adding に, so:

自由な → “free” (adjective)
自由に → “freely” (adverb)

In the sentence:

自由に modifies the verb 言える (“can say”), so it means “to say (something) freely.”

So 自由に意見を言える = “(they) can express their opinions freely.”

You would not say 自由な意見を言える for this meaning.
自由な意見 would mean “a free opinion” (a type of opinion), not “to express opinions freely.”

What does 言える mean exactly, and how is it made from 言う?

言う = “to say / to speak / to express.”
言える is the potential form of 言う, meaning “can say / be able to say.”

Formation: for 五段 (u‑verbs) like 言う, potential form is made by changing う → える:

言う → 言える (can say)
書く → 書ける (can write)
行く → 行ける (can go)

So 意見を言える = “can express (one’s) opinions.”

In longer, more literal style you could also say 意見を言うことができる, but 言える is shorter and very natural.

Why is it 意見を言える and not 意見が言える?

Both 意見を言える and 意見が言える are actually possible, but there is a nuance:

Base verb usage:
- 意見を言う is the standard pattern:
  “to say / express an opinion” → X を言う
- When you make the potential form, you can keep を:
  意見を言える = “(people) can express their opinion(s).”
が with potential verbs:
For many verbs, when you use the potential form, it’s common to switch the object marker from を to が:
- 日本語が話せる (can speak Japanese)
- 漢字が書ける (can write kanji)

So:

意見を言える emphasizes the action of expressing opinions.
意見が言える focuses a bit more on “opinions (themselves) can be said.”

In this sentence, 意見を言える社会 sounds very natural and is probably slightly more common, but 意見が言える社会 would also be understandable and not strange.

How does 意見を言える社会 work grammatically? Why is the verb phrase before 社会?

意見を言える社会 is an example of a relative clause in Japanese.

Structure in Japanese:
[Clause] + Noun

意見を言える = “(people) can say opinions”
社会 = “society”

In English, we need a relative pronoun and put the clause after the noun:
“a society where people can express (their) opinions.”

In Japanese, the entire phrase 意見を言える comes before 社会 and directly modifies it, with no relative pronoun:

意見を言える社会
literally: “opinion‑can‑be‑said society”
→ “a society where (people) can express opinions”

Key points:

No words like “that,” “which,” or “where” are needed.
The subject (“people / anyone”) is omitted because it’s obvious from context and from 誰でも earlier in the sentence.

What does the は after 社会 do here?

The は after 社会 is the topic marker.

Full chunk: 意見を言える社会は大切だと思います。

It means:

“As for a society where you can express opinions, I think it’s important.”

Function of は:

It takes 意見を言える社会 (“a society where opinions can be expressed”) and makes it the topic of the statement.
The rest of the sentence (大切だと思います) is a comment about that topic.

So the structure is:

Topic: 意見を言える社会は
Comment: 大切だと思います (“is important, I think”)

Why is it 大切だ and not 大切です before と思います?

Before と思います, Japanese almost always uses the plain form of the word being “thought.”

The pattern is:

(plain form) + と思います

Examples:

行くと思います (I think [someone] will go)
難しいと思います (I think it’s difficult)
大切だと思います (I think it’s important)

大切 is a na‑adjective, so its plain “is” form is 大切だ.

Using 大切ですと思います is unnatural because it mixes the polite です inside the quoted part. Instead:

Put the inner sentence in plain form: 大切だ
Make the verb 思います polite to match the overall politeness level.

So:

大切だと思います = natural and correct.
大切ですと思います = ungrammatical / unnatural.

What is the role of と in 大切だと思います?

Here と is the quotation particle.

It marks the content of what is being thought, said, heard, etc. Think of it as marking the “that …” clause in English:

大切だ = “it is important”
大切だと思います = “I think (that) it is important”

Same pattern with other verbs:

明日行くと言いました。
“He said that he will go tomorrow.”
静かだと感じます。
“I feel that it is quiet.”

So と here means “that” in the sense of “I think that …”

Why does the sentence end with 思います instead of just 大切です?

Ending with 大切です is a direct statement:

これは大切です。 = “This is important.”

But 大切だと思います introduces a nuance:

It turns the statement into the speaker’s opinion.
It sounds a bit softer, less absolute, a little more polite/modest.

So:

意見を言える社会は大切です。
“A society where one can express opinions is important.” (firm statement)
意見を言える社会は大切だと思います。
“I think a society where one can express opinions is important.”
(explicitly presenting it as your view)

In many contexts, Japanese speakers prefer 〜と思います to avoid sounding too blunt or dogmatic.

Why is there no 私 in the sentence? How do we know who thinks this?

Japanese often omits the subject when it is clear from context.

The full idea would be:

私は、意見を言える社会は大切だと思います。 “As for me, I think a society where one can express opinions is important.”

But:

私は is obvious when you say 思います in a normal conversation (it’s usually “I” unless context clearly says otherwise).
To avoid repetition and keep sentences short, Japanese tends to drop pronouns like 私, あなた, etc, whenever possible.

So:

The subject “I” is understood, even though it’s not written.

Could you say 誰も自由に意見を言える社会 instead? What would that mean?

If you say:

誰も自由に意見を言える社会

Grammatically, this is strange because 誰も normally pairs with a negative verb:

誰も言えない = “no one can say (it)”

So:

誰も … 言える is contradictory: “no one … can say.”

If you really wanted to say “a society where no one can freely express their opinion,” you’d say:

誰も自由に意見を言えない社会
“a society where no one can freely express their opinion”

For the intended positive meaning (“a society where anyone can…”), you must use 誰でも.

What is the difference between 自由な社会 and 自由に意見を言える社会?

They overlap in idea but are not identical:

自由な社会
“a free society” (very broad, general; could refer to many kinds of freedom: speech, movement, religion, etc.)
自由に意見を言える社会
“a society where you can freely express your opinions”
→ very specific, talking about freedom of expression / speech.

So the original sentence is focusing particularly on freedom to express opinions, not just “freedom” in a vague or broad sense.

Can we replace 言える with 言うことができる? Is there any difference?

Yes, you can say:

誰でも自由に意見を言うことができる社会は大切だと思います。

This is grammatically correct. The difference is mainly style and nuance:

言える
- Short, natural, common in everyday speech.
- Slightly more casual/neutral.
言うことができる
- Longer, somewhat more formal or explanatory.
- Slightly emphasizes the possibility/ability in a more explicit way.

In most normal spoken and written contexts, 言える is perfectly natural and preferred for being concise.

Why is 自由に placed before 意見を言える? Could it go somewhere else?

自由に is an adverb modifying the verb 言える, so it naturally appears directly before the verb phrase:

自由に意見を言える
“can freely express opinions”

You could also slightly rearrange things like:

意見を自由に言える社会

This is also grammatical and natural, with essentially the same meaning. The focus shifts very slightly:

自由に意見を言える社会 → feels like “a society where (people) can express opinions freely” (freedom → opinions).
意見を自由に言える社会 → feels like “a society where (people) can freely express opinions” (opinions → they can be expressed freely).

Both are acceptable. The original ordering is very typical and clear.