Incorrect understanding and concept possession

Tyler Burge has argued that an incorrect understanding of a word can be sufficient for possessing the concept the word literally expresses. His well-known ‘arthritis’ case involves a patient who understands ‘arthritis’ incorrectly, but who nevertheless, according to Burge, possesses the concept arthritis. Critics of Burge have objected that there is an alternative concept that best matches the patient's understanding and that this, therefore, is the patient's concept. The paper first argues that Burge's response to this objection is unconvincing. A better response is then developed. It is argued that there is no alternative concept that matches the incorrect understanding, since the patient thinks he has a partial understanding. This, together with points about ordinary psychological explanation and modes of presentations of concepts, establish that it is impossible to undermine Burge's social externalism by appealing to the idea that an alternative concept matches the incorrect understanding.