We examine the prospects for finding "best possible" or "ideal" computing machines for various learning tasks. For this purpose, several precise senses of "ideal machine" are considered within the context of formal learning theory. Generally negative results are provided concerning the existence of ideal learning-machines in the senses considered.
Osherson, Daniel N.; Stob, Michael; and Weinstein, Scott, "Ideal learning machines" (1982). University Faculty Publications and Creative Works. 523.