Final answer:
The movement toward abstraction in mid-19th century European art, exemplified by Manet's work, was catalyzed by the rise of Realism, which depicted contemporary life with authenticity, and the emergence of Impressionism, with its focus on light, color, and momentary impressions.
Step-by-step explanation:
The mid-19th century in Europe was marked by significant shifts in art, leading to a movement toward abstraction that can be seen in works such as Édouard Manet's Le déjeuner sur l'herbe. The two main catalysts for this movement were the advent of Realism and the development of Impressionism. Realism, as a reaction against Romanticism, portrayed life as it was, often depicting the contemporary world with all its flaws. This was in part a response to the changes brought about by industrialization and political revolutions. Realist artists such as Manet, who painted scenes of everyday life using loose brush strokes and simplified details, bridged the gap to Impressionism.
Impressionism, with artists like Claude Monet and Pierre-Auguste Renoir, evolved from Realism and reflected an interest in painting landscape and contemporary life. This movement emphasized capturing light, color, and momentary impressions of scenes, often with a focus on leisure activities and outdoor settings, painted en plein air. These revolutionary methods of using brushstrokes and synthetic pigments extended the ideas of Realism into new explorations of visual experience.