Fodor's arguments for a "language of thought" make sense (see his book of the same name). In a nutshell, thought seems to be productive – out of given concepts, we can always construct new ones, e.g. arbitrary nestings of "the mother of the mother of ..." – systematic – knowing certain concepts automatically leads to the ability to construct other concepts, e.g. knowing the concept "child" and the concept "wild", I can also represent "wild child" – and compositional, e.g. the meaning of "wild child" is a function of the meaning of "wild" and "child".