Link to critique of pure reason: http://www.fullbooks.com/The-Critique-of-Pure-Reason11.html
You need to write an essay on this quote; let's begin by posting the drafts first. Read the page in the link and some background reading about Kant from SEP.
You need to dedicate enough argumentation to what Kant said and why. That could be followed by your own comments about the topic; however dont skip his reasoning no matter if you justify it or not.