Why can’t Human eye focus on two objects at once?
Vision is a brain phenomenon not eye phenomenon. The brain behaves like LCD screen of a camera. Our vision is based on three dimensional constuction of images. The depth length and breadth are configured by the optic nerves. The eyes behave like a camera which projects the image to the screen which is the brain. The eyes cannot move independently. Learning this type of vision from childhood is due to phenomenon called ocular Fixation. These impressions are fixed in the brain in region called occipital cortex which is in the rear portion of the brain.
If there is paralysis of eye muscles we can move our each eye independantly, this condition called squint. For persons with squint the vision will appear double this image will be horrid to see and added to that true image will be bright and false image will be dull. So the ultimate reason for not able to view two objects is both eyes the eyes create three dimensional image of same object and project it to the eye