Full Idea
Time and space, Kant concluded, were 'ideal' since they could not be objects of direct sensory experience, and therefore had to be available only as 'pure' representations. ...Hence time and space were not 'objects' out there in the world.
Gist of Idea
We have no sensual experience of time and space, so they must be 'ideal'
Source
report of Immanuel Kant (Critique of Pure Reason [1781]) by Terry Pinkard - German Philosophy 1760-1860 01
Book Reference
Pinkard,Terry: 'German Philosophy 1760-1860' [CUP 2002], p.25
A Reaction
Put like this it sounds like a crazy application of empiricism, but demanding that space and time are experienced by the 'senses'. Can't we way that we experience them, but not through any particular sense? Kant at his most idealist.