New readings and all the posts helped me immensely to understand. But now I somewhat of a disagreement with definition of "a priori claim" and the example of knowing a triangle. All our basic shapes and alphabet are taught to us and we begin to recognize the word that goes with the shape or letter and then progress to drawing/writing the learned shapes, words, letters--so I contend that this learning IS a sensory function. Do 4 and 5 year olds really understand sides of equal length? They learn circle, box, triangle, diamond and progress from there.