What is an outdated theory based on the consensus of the scientific community?

One outdated theory is the concept of phlogiston, which was once believed to be a substance released during combustion. According to this theory, all flammable materials contained phlogiston, which was released when they burned, resulting in ash or residue. The theory was widely accepted until the late 18th century when Antoine Lavoisier's work on oxygen and the chemical processes of combustion led to its rejection, establishing the modern understanding of oxidation. Today, the scientific community recognizes combustion as a chemical reaction involving oxygen rather than the release of phlogiston.