Not your brain so much, but the combination of the non-mapping of phosphors to pixels, and the fact that the electron beam ramps up and down, rather than instan

Not your brain so much, but the combination of the non-mapping of phosphors to pixels, and the fact that the electron beam ramps up and down, rather than instantly turning on or off, causes the pixels to be softened, moreso across a scanline than between them. Your brain helps too, but in the same way that it helps with every color display device that uses RGB or some variant. Get close enough and you can perceive the individual phosphors or subpixels in either case.