In this paper, I make two theoretical claims: (i) For some form to be grammatical in language L, it is not necessary that the form satisfy all constraints that are active in L, i.e. even grammatical forms can violate constraints. (ii) There are degrees of ungrammaticality, i.e. not all ungrammatical forms are equally ungrammatical. I first show that these claims follow straightforwardly from the basic architecture of an Optimality Theoretic grammar. I then show that the surface sound patterns used most widely in formal phonology cannot be used to test the truth of these two claims, but argue that results from speech processing experiments can. Finally, I discuss three experiments on the processing of non-words of the form [stVt], [skVk] and [spVp] in English that were designed to test these claims, and show that both claims are confirmed by the results of the experiments.