Synonyms for «fundamental difficulty»

Synonyms for individual words can be found below.

The most fundamental difficulty, however, has been that no one knows exactly how severe the problem is. (scientificamerican.com)
But there remains one fundamental difficulty which concerns the principal thesis of Duméry's system. (religion-online.org)
Quantum theory has been in fundamental difficulty from the beginning. (religion-online.org)
(see all sentences)