When Has to is used for certainty i.e. Watson has to be a fine player.
Watson has to be a fine player. and
Watson is a fine player.
What is the difference between these two? Would you please explain?
If say like this
This answer has to be correct. and
This answer is correct.
'This answer has to be correct' is your opinion — however certain you are about it.
'This answer is correct' is a fact.
(Either the speaker's opinion or the repetition of a commonly-held opinion that the speaker agrees with and expects the listener to agree with: 'Let It Be has to be the greatest rock song ever written' - that's an example, by the way, not a view I'd care to defend [although I think that song's pretty good]. )