 The challenges for social models of disability for justice may seem greatest for intellectual and psychiatric impairments, as well as for complex physical impairments such as fibromyalgia, multiple chemical sensitivity, and other conditions that radically and unpredictably affect energy, stamina, and functioning (Wendell 1989, 1996; Davis 2005). First, these conditions strikingly display both aspects of impairment, as markers for stigma and as sources of functional limitation (see SEP entry,  disability: definitions, models, experience).  Cognitive and psychiatric impairments evoke some of the strongest prejudice and all present some of the most difficult functional limitations, e.g., on the capacities to engage in practical reasoning, to recognize the intentions and attitudes of other people, or to participate in shared activities.Second, some theorists contend that these conditions pose more of a practical challenge for the social model than even the most severe physical disabilities, in part because the measures required for greater inclusion are not as concrete or tangible, and may demand greater imagination to envision and  implement.[5] 