Of all the ideas that human reason can form, Hooke considered the simplest and the most fundamental to be the geometrical concepts of point and straight line. Undoubtedly we are able to think these, but the naïve consciousness takes for granted that it also perceives them as objective realities outside itself, so that thoughts and facts correspond to each other. We must now ask, however, if this belief is not due to an optical deception. Let us turn to the microscope and see what point and line in the external world look like through it.