Consider the following sentence groups:

"Tom guesses it will rain."
"It may rain."
"The author guesses it will rain."

"Dick doubts it will rain."
"It will hardly rain."
"The author doubts it will rain."

"Harry knows it will rain."
"It must rain."
"The author knows it will rain."

"Harry denies that it's raining."
"It's not raining."
"The author denies that it's raining."

It seems that the ideas of "may", "will hardly", "must", "not", etc.,
are logically equivalent to "the author <verb>". Naturally, instead of
explicitly writing "the author", the verb could simply receive a
particular form to mean that it's an opinion of the author or a fact
that doesn't depend on the text character's opinions. Apparently,
English can do this with adverbs:

"Possibly, it will rain."
"Hardly, it will rain."
"Probably, it will rain."
"Negatively it's raining." (I guess this one is not really said.)

Do any nat or conlangs express this type of ideas by means of a
specific conjugation of verbs such as "guess", "believe", "deny",
"affirms", etc., instead of using "might", "probably", "not", "yes",

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