I have been studying about the human eye and it's working in school for some time. I came across something. I have been taught that the image formed on the retina of the eye by the lens is inverted and the image is made erect by the brain so as for correct perception. But how does the brain know what is erect or inverted? Why doesn't it just keep the image as it is? Please note that I am asking why the brain reverses the image and not about the nature of image formed on retina.