Image processing by the eye is treated as a classical example of concatentated linear filters followed by a sampling operation. The first filter is optical and is characterized by an optical point-spread function. The second filter is neural and is characterized by the neural point-spread function, which is shown to be related to the receptive fields of retinal neurons. Sampling renders the internal "neural image" a discrete signal subject to the effects of aliasing. Conditions responsible for aliasing are formulated in terms of the amount of overlap of retinal samplers. Evidence of aliasing in human vision is presented along with a simulation of an aliased neural image in the peripheral visual field.