Seeing Cezanne

The division between Impressionism and Post-Impressionism seems somewhat contrived. It's as if the line was arbitrarily drawn down the middle of a larger movement of art, and the details of the distinction filled in later to justify the line. The cyclic nature of artistic rebellions is not apparent here; at least, not nearly as apparent as the reaction of the Impressionists against classical artwork, or as drastic as the invention of Cartesian perspective. Instead of a dramatic reaction, the progression from Impressionism to Post-Impressionism is fairly smooth. The gaps between the "diametrically opposed"(160) principles of each movement are bridged easily by Cezanne.
The main difference seems to be the idea of representation versus expression. In both cases it is a matter of the artist's intent. If two artists create a nearly identical piece of artwork, but with radically different intentions, either to represent or express, how can the viewer differentiate the two without knowing the intent of either artist? Which is more important in classifying artwork, the artist's intent or the viewer's interpretation?