A method is provided for formulating a personal cleansing composition. At least one primary surfactant, at least one secondary amphoteric and/or nonionic surfactant, at least one humectant, and at least one polymeric and/or quaternary conditioner are selected, each of these components having a natural and renewable resource origin. The primary and secondary surfactants are combined with the at least one humectant and the at least one conditioner in a final composition that includes the combined primary and secondary surfactants at less than about 14 wt. %, and includes the combined at least one humectant and at least one conditioner at less than 5.5 wt. %. After forming the final composition, an optimum performance index (OPI) is determined for the composition to ensure that the composition has an OPI of at least about 5.450. The OPI is calculated as: OPI=3÷((solids wt.%+Zein score)÷performance grade).