Full Idea
For Kant, experience is relativised to a categorial framework, but there is no further relativisation, at least in any deep respect, to a plurality of possible conceptual schemes.
Clarification
'Categorial' means involving categories
Gist of Idea
For Kant, experience is relative to a scheme, but there are no further possible schemes
Source
report of Immanuel Kant (Critique of Pure Reason [1781]) by Robert Fogelin - Walking the Tightrope of Reason Ch.3
Book Reference
Fogelin,Robert: 'Walking the Tightrope of Reason' [OUP 2004], p.72
A Reaction
This point is enlarged nicely by Davidson, in his view that we could make no sense of a different 'conceptual scheme' (Idea 6398). Kant's resistance to speculation prevents him imagining how it might be to be an angel, or an alien, or a Hopi.
Related Idea
Idea 6398 Different points of view make sense, but they must be plotted on a common background [Davidson]