What idea did Alberta introduce in his famous work of art theory On Painting?

In his influential work "On Painting," Alberto Alberti introduced the idea that painting is a science as well as an art, emphasizing the importance of perspective and proportion in creating realistic representations. He argued that artists should study nature and apply mathematical principles to achieve harmony and balance in their compositions. Alberti also highlighted the role of the viewer in interpreting art, suggesting that a painting should engage the observer's imagination and emotions. This framework laid the groundwork for the development of Renaissance art theory.