inwardly and that had to be translated into a picture. Sensation is another key term in Cézanne's vocabulary. First of all, he meant visual perception in the sense of “impression”, i.e. an optical sensory stimulus emanating from the object. At the same time, it includes the emotion as a psychological reaction to what is perceived. Cézanne expressly did not place the object to be depicted at the center of his painterly efforts, but rather the sensation: "Painting from nature does not mean copying the object, it means realizing its sensations." The medium that mediated between things and sensations was the colour, although Cézanne left it open to what extent it arises from things or is an abstraction of his vision. Cézanne used the third term réalisation to describe the actual painterly activity, which he feared would fail to the end. Several things had to be “realized” at the same time: first the motif in all its diversity, then the feelings that the motif triggered in him, and finally the painting itself, the realization of which could bring the other “realizations” to light. "Painting" therefore meant letting those opposing movements of taking in and giving, of "impression" and "expression" merge into one another in a single gesture. The "realization in art" became a key concept in Cézanne's thinking and acting. Dating and cataloguing The sometimes longer dates for creation in the catalogues of Cézanne's works do not always indicate that the exact dating cannot be clarified, even if Cézanne rarely dated his pictures, especially since he worked on some pictures for months if not years before he was satisfied with the result. The artist himself regarded many of his paintings as unfinished, for painting was a never-ending process for him. Cataloging Cézanne's works turned out to be a difficult task. Ambroise Vollard made the first attempt, a multi-volume photo album, similar to his catalogue of Renoir. Vollard's catalogue never materialized however. Georges Rivière, the father-in-law of Cézanne's son published a biography of the artist in 1923 (Le Maître Paul Cézanne) that included a chronological and annotated list of many of the painter’s works. Conceived by the art dealer Paul Rosenberg, the first complete catalogue raisonné was published by Lionello Venturi in 1936. The two volume Cézanne: Son Art, Son Oeuvre became the definitive catalogue of the artist's work for over five decades, although requiring a supplement as additional works were discovered