The present article candidly states the incremental impact of nonlinear thermal radiation on heat transfer enhancement due to Darcy–Forchheimer flow of spinel-type MnFe 2 O 4 -Casson/water nanofluids due to a stretched rotating disk. In present contest, the entropy generation approach is highlighted specially as a powerful tool for the analysis of the brain function, in accordance with the theological and philosophical approach of Saint Thomas Aquinas. The some of the results of the present study that strengthening of permeability and Casson parameter contribute to the diminution of radial and tangential velocity profiles and yield shrinkage of the related boundary layers. An increase in thermal radiation leading to more heat propagating into the fluid thereby improves the TBL. Fluids with non-Newtonian behavior contribute greater entropy generation rate compared to Newtonian fluids. The most significant outcome is that the entropy generation makes a real contribution to the brain function or analysis of the function of the brain.