The phrase "a challenging notion" is correct and usable in written English.
It can be used when discussing an idea or concept that is difficult to understand or accept.
Example: "The theory presented in the lecture was a challenging notion that sparked much debate among the students."
Alternatives: "a difficult concept" or "a complex idea."
Today, we're used to the nuclear family breaking up, then it was a challenging notion.
Even talking about sex-related matters with their doctor is a challenging notion.
These findings are consistent with Barab and Hay (2001), who reported participants in an apprenticeship program had difficulty grappling with alternative findings, because such findings presented a challenging notion to the students who "all too often view science as getting the correct answer" (p. 96).
The cubist villas he designed in and around Paris in the 1920s were the embodiment of his challenging notion that a house is "a machine for living in".
The success of each of these diverse approaches depends on one common but often challenging notion -- a willingness to talk about money.
It's on the autistic spectrum and has a significant impact on a person's social and behavioral abilities, making the already challenging notion of daily communication even more of an uphill climb.
"In Judaism, I'm faced with the equally challenging notion that the flesh became words".
In bold moves that have garnered praise, emulation and controversy, Mr. Botstein has promoted a three-part agenda: rethinking musical programming and the concertgoing experience; expanding the orchestral repertory and challenging notions of an accepted canon; and bridging the often huge gap between the world of the performing arts and the university.
Just a year and a half removed from his first, tentative moments of testing his prosthesis, Wallace is now challenging notions of how long those who lose a limb need before competing at a high level.
But the artist seems, rather, to be challenging notions of what is picturesque.
