 Despite its initial appeal, objections to the standard theory have been made by theorists from both philosophy and linguistics. In summary, the objections build on the idea that “if” in English does not always express a uniform kind of condition. If different kinds of conditions are expressed by the word “if”, the objectors argue, then it would be wise to uncover these before engaging in attempts to formalize and systematize the concepts of necessary and sufficient. In trying to show that there is an ambiguity infecting “if”-sentences in English, critics have focused on two doctrines they regard as mistaken: first, that there is a reciprocity between necessary and sufficient conditions, and, second, that “if p, q” and “p only if q” are equivalent.