  Len Doyal and Ian Gough (1991) offer a highly influential account that aims to connect philosophical and empirical disciplines. On their view, needs are universalizable preconditions that enable non-impaired participation in any form of life. Physical health and autonomy (by which they mean the mental competence to deliberate and choose) are the two basic needs. An additional class of intermediate needs connect these two basic needs with social science knowledge that can be useful in measuring needs fulfilment. The intermediate needs are nutritious food and clean water, protective housing, a non-hazardous work environment, a non-hazardous physical environment, appropriate health care, security in childhood, significant primary relationships, physical security, economic security, appropriate education, safe birth control, and safe child-bearing. Armed with these intermediate needs they drill down even further, offering specific ideas about the kinds of metrics we should adopt to help gain a sense of whether needs are being met. These metrics are also helpful in measuring progress with respect to meeting needs over time.