The proof that impressions come first is derived from experience; for example, a man born blind has no ideas of colours.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“Complex ideas, on the other hand, need not resemble impressions. We can imagine a winged horse without having ever seen one, but the constituents of this complex idea are all derived from impressions. The proof that impressions come first is derived from experience; for example, a man born blind has no ideas of colours. Among ideas, those that retain a considerable degree of the vivacity of the original impressions belong to memory, the others to imagination. There is a section (Book I, Part I, Sec. VII) “Of Abstract Ideas,”” source