It is the doctrine I believed to be right .
It is the doctrine I believed was right.
It is the doctrine I believe is right.
What is the difference between "to be right," "was right," and "is right" used in this sentence? And why using "was right" and "is right" possible? Is it because it is used the same way as "doctrine which I think was right"?
Also, is it possible to change this question
What would you predict the mass of rocket to be?
to this
what would you predict the mass of rocket is?
since the answer would usually be "I predict that the mass of rocket is…", not this: "I predict the mass of rocket to be." Is it possible? Thank you!
Best Answer
All three of these sentences are grammatical, and they all mean the same thing.
Further, all three lack the same thing -- a relative pronoun marking a relative clause:
It is the doctrine that/which I believed to be right.
It is the doctrine that/which I believed was right.
It is the doctrine that/which I believe is right.
All three of these sentences are grammatical and synonymous as well.
Notice also that in all three relative clauses, the relative pronoun, whichever it is,
is extracted from a clause below the believe clause; so let's reconstruct that originals:
Once again, all grammatical and all synonymous. The relative clause formation rule extracts the doctrine and then deletes the relative pronoun because it's not the subject of its relative clause
(I is already the subject).
This leaves a gap between I believed and its object clause, which is reduced to a verb phrase only.
So why are there three variants? Because believe can take an infinitive complement
I believed the doctrine to be right.
as well as a tensed that-clause, of either tense:
I believed (that) the doctrine was right
I believed (that) the doctrine is right
and here all the clause-marking that's have been deleted.
They can't occur with an infinitive, only with a tensed clause.