The history of poetry in all countries, but particularly in France, registers a kind of oscillation between two poles, being diluted into prose at one extreme or distilled into an essence unapprehendable by the mind on the other. Two names will make this clearer. Voltaire represents the first pole; his formula (which Sainte-Beuve quotes several times) for ensuring himself of the quality of French verses, was to put them into prose....Mallarmé represents the other pole. Upon being criticized for his obscurity he replied, paradoxically but in all truth, that he was really perfectly lucid. Indeed, since his poetry did not propose "to be understood" it could not be obscure, and since it offered itself to the taste of the reader, such as it desired to be, it could rightly consider itself lucid exactly as it was.
Etienne Gilson, Forms and Substances in the Arts, pp. 216-217.