Nonetheless, there are several features of CET which  suggest it should be regarded as less well established than CT.  Paramount amongst these is that we do not as yet know whether \(\textbf{P}\) is properly contained in complexity classes such as \(\textbf{NP}\) which appear to contain highly intractable problems.  The following additional caveats are also often issued with respect to the claim that the class of computational problems we can decide in practice neatly aligns with those decidable in polynomial time using a conventional deterministic Turing   machine.[10]