The phrase "are only conceivable" is correct and usable in written English.
It can be used when discussing ideas, scenarios, or concepts that can be imagined or thought of, but may not necessarily exist in reality.
Example: "In a world without technology, certain advancements are only conceivable in our wildest dreams."
Alternatives: "can only be imagined" or "are merely theoretical".
Perhaps it is only conceivable, and not really possible, that there are zombies or inverted qualia.
However, the importance of oncotic pressure in the limitation of flux is only conceivable if the barrier is intact.
My first bra was the grayish-white of recycled paper, and it's only conceivable purpose was to add warmth beneath my matching tunic and stirrup-leggings ensembles -- there definitely wasn't anything to support back then.
The implementation of individual screening is only conceivable if a large amount of information is given to prescribing physicians.
"After Labus lost the first round, there were only two conceivable outcomes in the runoff -- a Kostunica victory and a failed election.
If Americans sat on their sofas at 9pm last night thinking of that debate as an interview for the job Joe Biden described, then there was only one conceivable winner.
It is not only conceivable that some samples that were scored negative would have been positive with a higher peptide dose than that used in the assay (25 μ M), but also the opposite scenario is conceivable.
If Nocera had looked at alternatives that many of us have been suggesting and if he still concluded that helping rich guys get richer was the only conceivable strategy, his attitude might be acceptable.
I suspect the reason for this tunnel vision is western hubris: a belief that our modernity is the only conceivable one, that our political and cultural arrangements will ultimately be adopted by everyone else.
McTaggart holds that we can conceive of nothing that is not a material object, a sense-datum, or something spiritual, and since the first two kinds of objects are metaphysically impossible, the hypothesis of idealism is the only conceivable hypothesis left standing.
