must be that

[jiang]

Dear teachers,

I am not familiar with the structure of the sentence "It must be that all children are actors".

I know I can say "I must work hard". You mustn't do that.
He must be reading a book right now.
It must have rained yesterday.

But can "it must be" followed by a that clause?

Looking forward to hearing from you.
Thank you in advance.

Jiang

[5jj]

1a. I must work hard.....
1b. You mustn't do that.
Obligation, necessity.

2a. He must be reading a book right now.
3b. It must have rained yesterday.
Logical certainty.

3a. It must be (the case) that all children are actors.
Logical certainty.

The wording of 3a removes the potential ambiguity in 3b. All children must be actors. That could be obligation or logical certainty. Only context would make the meaning of 3b clear.

[jiang]

Hi 5jj,

Thank you very much for your explanation. Now I understand it.

Jiang

1a. I must work hard.....
1b. You mustn't do that.
Obligation, necessity.

2a. He must be reading a book right now.
3b. It must have rained yesterday.
Logical certainty.

3a. It must be (the case) that all children are actors.
Logical certainty.

The wording of 3a removes the potential ambiguity in 3b. All children must be actors. That could be obligation or logical certainty. Only context would make the meaning of 3b clear.