For me, weaning was as mysterious a concept as figuring out how to breastfeed in the first place. (romper.com)
In many ways, marketing may be the most mysterious concept the self - published author faces. (draft2digital.com)
Mysterious concepts like that of the racial unconscious, quite inexplicable as they are usually presented, become fully intelligible in the context of Whitehead's philosophy. (religion-online.org)