Full Idea
That complete space …has three dimensions, and that space in general cannot have more, is built on the proposition that not more than three lines can intersect at right angles in a point.
Gist of Idea
Space must have three dimensions, because only three lines can meet at right angles
Source
Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 285)
Book Reference
Kant,Immanuel: 'Prolegomena to Any Future Metaphysic', ed/tr. Lucas,Peter G. [Manchester UP 1971], p.40
A Reaction
Modern geometry seems to move, via the algebra, to more than three dimensions, and then battles for an intuition of how that can be. I don't know how they would respond to Kant's challenge here.