Perception is what is given in experience.
What people do desire is what is given in experience. In both natural and moral philosophy claims must be justified by appeals to experience. Mill appeals to empirical evidence to support his claim that human pleasures include not only pysical pleasures but also the pleasures of the intellect, feelings, imagination and the moral sentiments. Human beings have faculties which enable them to experience these higher pleasures. Mental pleasures are intrinsically superior to physical pleasures, as well as circumstantially.