Issues of intergenerational equity, irreversibility of environmental change, uncertainty of long-term outcomes, and sustainable development guide ecological economic analysis and valuation.[6] Ecological economists have questioned fundamental mainstream economic approaches such as cost-benefit analysis, and the separability of economic values from scientific research, contending that economics is unavoidably normative, i.e. prescriptive, rather than positive or descriptive.[7] Positional analysis, which attempts to incorporate time and justice issues, is proposed as an alternative.[8][9] Ecological economics shares several of its perspectives with feminist economics, including the focus on sustainability, nature, justice and care values.[10]