 Scientia in natural philosophy would require knowledge both of real essences and of their necessary connections among qualities, yet neither is possible for human beings, Locke concludes. One obstacle to scientia, then, is that real essences escape us. God has given us sensory capacities that are suitable for finding our way to the “market and exchange” and other practical needs, but are not suitable, as the “microscopical eyes” passage indicates, for detecting the minute parts of bodies.