The phrase "at once certain" is correct and usable in written English.
It can be used to express immediate confidence or assurance about something.
Example: "She was at once certain that she had made the right decision."
Alternatives: "immediately sure" or "instantly confident".
Russia had a breakthrough moment in 1991 — the totalitarian structures, the imperial structures, seemed hollow at the center once certain pressures were brought to bear, once certain freedoms were extended.
Russia had a breakthrough moment in 1991 the totalitarian structures, the imperial structures, seemed hollow at the center once certain pressures were brought to bear, once certain freedoms were extended.
It would be better, therefore, to say with Empedocles and any one else who may have maintained such a theory as his that the universe is alternately at rest and in motion: for in a system of this kind we have at once a certain order.
Combine trips to run several errands at once in certain areas of town.
The union wants to vote on the entire board at once, contending that certain conditions may warrant cleaning house.
Workers have multiple chat windows open at once, and when certain financial information pops up in one window, it can be routed immediately into spreadsheets containing financial models that, in turn, trigger buying decisions, Saint-Andre says.
I therefore at once summarily state certain dominant propositions which are to my mind not subject to be controverted, because, whatever may be the differences of opinion as to some of them, considered originally, they are all so conclusively established by the previous decisions of this court as to be now beyond dispute.
With the overhaul, Steller has added some new features like the ability to upload multiple photos and videos at once into a certain story.
I used to do what so many other women like me do - wear two sports bras at once or avoid certain exercises.
"There was such an inherent conflict in the scene itself: it was at once intellectual from certain quarters, and then there was a strong sense of parody, bands pushing past the furthest edge of the anti-societal things they could come up," Ewell says.
