Describe the accepted theory during redi's time explaining the origin of the flies

During the time of Fransesco Redi, the 17th century, people believed in spontaneous generation of organisms from non-living thing, or abiogenesis.

The people of that time believed that living things, such as flies, arise from non-living things spontaneously. Fransesco Redi challenged this belief and set up the famous fruit fly experiment to demonstrate that life comes from pre-existing life, and not from non-living things such as meat and fruit.