The phrase "a certain illusion" is correct and usable in written English.
It can be used when referring to a specific but not explicitly defined illusion or misconception that one might have about a situation or concept.
Example: "Many people live their lives under a certain illusion that success comes without hard work."
Alternatives: "a particular misconception" or "a specific delusion".
Brewer (2008) offers a disjunctivist account of certain illusions that he thinks need not be treated as cases of partial hallucination (e.g., the Mueller-Lyer illusion).
In the case of certain illusions, when an object looks to be a certain way that it isn't, a disjunctivist might place emphasis on the idea that this misleading appearance is publicly observable; for instance, it might be the sort of thing one is able to photograph.
(For an argument for the claim that accommodating certain illusions poses significant difficulties for the disjunctivist, see Smith 2010).
The general public will be informed of the results through lay science articles in local and national newspapers with the specific aim of creating a better understanding of this infection and eliminating certain illusions about the 'flesh-eating bacteria'.
And so was this paradox: that certain illusions were necessary to maintain the equilibrium of their lives.
Accordingly, he identifies reason as the locus of certain principles and propensities, and certain "illusions," which cooperate with misapplications of concepts and principles to create the errors already exposed in the Transcendental Analytic.
If you're actually going to survive in the system, tough it out for the long haul, certain illusions must be shed.
"This could be related to certain illusions they have: when they perceive sensations that actually come from themselves as alien," Böhme tells me.
It is, to a certain extent, an illusion.
While very common, beyond a certain point such illusions may lead to maladaptive persistence in unattainable goals [ 26, 29].
