Abstract

A fundamental issue in the philosophy of psychiatry is that of the reality of mental illness: is there any such thing as mental illness? The dominant means of resolving this issue—either for or against—is the likeness argument. This states that mental illness exists, or does not, depending on the extent to which putative mental illnesses (such as alcoholism or schizophrenia) are like universally accepted illnesses (such as pneumonia). To succeed, this argument has to assume (1) that the features of conditions such as schizophrenia will decide whether they are illnesses or not and (2) that the existence of these features can be determined independently of the question whether they are illnesses or not. Both assumptions can be questioned. A weaker objection to the likeness argument questions the first, but it is possible to overcome it. A stronger objection questions the second assumption, and is successful in undermining it. This also undermines the first assumption. As a result, the likeness argument will fail. Two major objections to the stronger objection are considered and accommodated.