CET is now widely accepted within theoretical computer science for reasons which broadly parallel those which are traditionally given in favor of Church’s Thesis.  For instance, not only is the definition of the class \(\textbf{FP}\) stable across different machine-based models of computation in the manner highlighted by the Invariance Thesis, but there also exist several machine independent characterizations of this class which we will consider in Section 4.  Such results testify to the robustness of the definition of polynomial time computability.