Semyon Semenovich, after putting on his glasses, looks at a pine tree and sees: on the pine tree, a villager is sitting and shaking his fist.
Semyon Semenovich, after taking off his glasses, looks at the pine tree and sees that there is no one sitting on the pine tree.
Semyon Semenovich, after putting on his glasses, looks at the pine tree and once again sees a villager sitting on the pine tree and shaking his fist.
Semyon Semyonovich, taking off his glasses, again sees that nobody is sitting on the pine tree.
Semyon Semyonovich, again after putting on his glasses, looks at the pine tree and again sees a villager sitting on the pine tree and shaking his fist.
Semyon Semenovich does not want to believe in this phenomenon, and so chooses to believe that it is an optical illusion.