Normal (geometry) Normal (geometry) In geometry, a normal is an object such as a line or vector that is perpendicular to a given object. For example, in two dimensions, the normal line to a curve at a given point is the line perpendicular to the tangent line to the curve at the point. In three dimensions, a surface normal, or simply normal, to a surface at a point "P" is a vector that is perpendicular to the tangent plane to that surface at "P". The word "normal" is also used as an adjective: a line normal to a plane, the normal component
When a white horse is not a horse horses, doesn't that mean that there are horses? For there to be white horses is for there to be horses. How could it be that the white ones are not horses? Advocate: If one wants horses, that extends to yellow or black horses. But if one wants white horses, that does not extend to a yellow or black horses. Suppose that white horses were horses. Then what one wants [in the two cases] would be the same. If what one wants were the same, then 'white' would not differ from 'horse.' If what one wants does not differ, then how