Veblen–Young theorem
In mathematics, the Veblen–Young theorem, proved by , states that a projective space of dimension at least 3 can be constructed as the projective space associated to a vector space over a division ring. Non-Desarguesian planes give examples of 2-dimensional projective spaces that do not arise from vector spaces over division rings, showing that the restriction to dimension at least 3 is necessary. Jacques Tits generalized the Veblen–Young theorem to Tits buildings, showing that those of rank at least 3 arise from algebraic groups. generalized the Veblen–Young theorem to continuous geometry, showing that a complemented modular lattice of order at least 4 is isomorphic to the principal right ideals of a von Neumann regular ring. Statement

A projective space S can be defined abstractly as a set P (the set of points), together with a set L of subsets of P (the set of lines), satisfying these axioms :
 Each two distinct points p and q are in exactly one line. Veblen's axiom: If a, b, c, d are distinct points and the lines through ab and cd meet, then so do the lines through ac and bd. Any line has at least 3 points on it. The Veblen–Young theorem states that  if the dimension of a projective space is at least 3 (meaning that there are two non-intersecting lines) then  the  projective space is isomorphic with the projective space of lines in a vector space  over some division ring K.

References

Theorems in projective geometry
Theorems in algebraic geometry