Socrates rather famous said the opposite...he only knows that he does not know.
The claim that philosophers sometimes make is that you can’t just substitute science for philosophy because philosophy deals with a wider range of problems. But that isnt the same as claiming to have The Truth about them all.
That’s basically what they’re for, yes, and certainly they claim to have more Truth than any other field, such as “mere” sciences.
Is that what they say?
ETA
Socrates rather famous said the opposite...he only knows that he does not know.
The claim that philosophers sometimes make is that you can’t just substitute science for philosophy because philosophy deals with a wider range of problems. But that isnt the same as claiming to have The Truth about them all.