[simonh]

Either it is possible to know certain things from rational consideration alone without reference to the evidence of our senses, or it isn't.

[coldtea]

Similarly, either it is possible to know certain things from observation of sensory input alone without reference to a ration framework of consideration, or it isn't.

And seem both cases seem unlikely, it seems that empiricism and rationalism are more complimentary (AND) than XOR.