It is evident, however, that our justification for such classifications can be no stronger than the stock we place in CT itself. One form of evidence often cited in favor of the thesis is that the coincidence of the class of functions computed by the members of \(\Lambda, \mathfrak{R}\) and \(\mathfrak{T}\) points to the mathematical robustness of the class of recursive functions. Two related forms of inductive evidence are as follows: (i) many other independently motivated models of computation have subsequently been defined which describe the same class of functions; (ii) the thesis is generally thought to yield a classification of functions which has thus far coincided with our ability to compute them in the relevant ‘in principle’ sense.