The phrase "already opaque" is correct and usable in written English.
It can be used to describe something that has become unclear or difficult to understand at an earlier point in time.
Example: "The explanation was already opaque, making it hard for the students to grasp the concept."
Alternatives: "previously unclear" or "initially ambiguous".
The Birmingham bombings appeared to fall into a grey area of this already opaque understanding.
Bathing suits are made to be worn in public, so they're already opaque in the right places.
The law will make an already opaque government more so by threatening to jail journalists, up to five years, for doing their job in an "invalid" and "wrongful" manner.
The message from the Federal Reserve merely muddied an already opaque process.
The early voting data starting to roll in adds layers of complexity to an already-opaque picture.
Unfortunately, in "Jonas" the swirling, incantatory language often obscures what is already an opaque narrative.
He has started reviewing deals for any signs of money laundering, with bank chiefs already quizzed over opaque agreements fronted on behalf of politicians.
But a growing number of scientists, as well as fishermen like Mirarchi, recognize that another factor -- global warming -- is sending the already delicate and opaque mechanics of marine ecosystems into a period of rapid flux.
The Fifa president, Sepp Blatter, already under fire over the opaque bidding process, declined to comment on the three Fifa executives alleged to have taken bribes.
This blunder shuffled canons from the top and bottom rows together like playing cards, making the already obscure text even more opaque.
To sum up, then, Sellars' attempt to tie existence to temporal notions, when properly relativized, is either a bland re-statement of what special relativity tells us already about simultaneity or an opaque statement about relativized existence.
