They [some special kind of philosophers] think it a reproach to all literature, that philosophy should not yet have fixed, beyond controversy, the foundation of morals, reasoning, and criticism; and should for ever talk of truth and falsehood, vice and virtue, beauty and deformity, without being able to determine the source of these distinctions.
It's from Hume's "Enquiry concerning human understanding", so the it's a little bit old.
I have troubles with understanding this passage.
What does the construction "should not yet have" express? Let's insert this construction in some simple sentence: "John should not yet have cleaned his room". I have three suggestions about its meaning, please comment on their rightness:
John was not yet obliged to clean his room.
This is the same as "John has not yet cleaned this his room". But then the role of "should" is unclear.
John had the obligation to clean his room but failed to fullfil that. In this case I'm gonna need you to explain me the syntax. Is then in this construction implied something like "but"? "Should [but] not yet have"?