Full Idea
In the 'Critique of Pure Reason' Kant shows that theoretical reason is unable to answer the questions of speculative metaphysics.
Gist of Idea
Kant showed that theoretical reason cannot give answers to speculative metaphysics
Source
report of Immanuel Kant (Critique of Pure Reason [1781]) by Christine M. Korsgaard - Intro to 'Creating the Kingdom of Ends' 'Intro'
Book Reference
Korsgaard,Christine M.: 'Creating the Kingdom of Ends' [CUP 1996], p.3
A Reaction
I don't think I really agree with Kant. We can draw very extended inferences from experience, but the process rapidly becomes exceedingly difficult. The concepts we have built up are rather piecemeal, and not really designed for the job.