Rousseau was a primitivist - he became an artist without additional training, simply because he felt an inner desire. He did not have a teacher who would show him the basics, and, trying, making mistakes, he discovered painting for himself, as a completely new science, as alchemy. Where others have long passed without stumbling, he found new pits and fell on old bumps.
Passing his path alone, he came to post-impressionism, in which primitivism did not look like an ugly encroachment on art (a primitive realist would look just like that), but as a logical development of the thought contained in it.
After all, post-impressionism did not cling to a momentary sensation and not to a possible full reflection of reality, but to search for the basis of being, the only answer to all questions. Just as mathematicians were looking for the only formula in the universe that would explain everything, so post-impressionists were looking for such a combination of movements and colors. Trying all the styles, mixing them and sharing them back, they did not see anything wrong with primitivism.
Rousseau's self-portrait is different from the portraits of his great predecessors. They sought to depict themselves as detailed as possible so that the descendants would not forget their appearance, Rousseau depicted himself almost satirically, as if kindly joking with himself. After all, officially, he was not an artist, but was a customs officer, and he is depicted like that - in the port, by the arriving ship, adorned with colored flags.
Behind him is a bridge, a lone man meets a ship, the sky is all in the clouds and a lone airship flies over it. The sun is hidden, sends out direct scarlet rays of glare, the city is visible in the distance, and Rousseau is standing in the middle of everything, dressed in a dark suit, holding a palette and a brush in his hands - like a symbol of his dream, which he made for himself an ambitious past.