Why did Democritus think qualitative differences were only apparent?

Democritus argued that qualitative differences—such as color, taste, or temperature—are merely apparent because they do not exist as inherent properties within the objects themselves. Instead, he posited that the physical world is composed entirely of atoms and the void, which are the only things that exist in reality.1

According to his atomic theory, atoms are homogeneous and differ only in quantitative, mechanical properties: shape, arrangement, position, and magnitude. What we perceive as qualities are actually the effects produced on our senses by the specific configurations and combinations of these atoms. For example, a sweet taste is caused by round atoms, while the sensation of color is determined by the position and shape of the atoms constituting a compound. Because these sensations result from the interaction between external atoms and the observer's soul, they are considered conventional rather than objective realities. Thus, Democritus reduced the complexity of the observable world to a purely mechanical system governed by necessity.12