According to Galileo, what defines the true nature of everything?

Galileo's philosophy emphasizes the distinction between primary and secondary qualities, with primary qualities being fundamental properties that exist independently of any observer's perception. In his view, primary qualities include attributes like shape, size, motion, and number—elements that can be measured and quantified. These qualities represent the inherent nature of objects in the physical world, allowing for a more objective understanding of reality.

In contrast, secondary qualities, such as color, taste, and sound, depend on the observer’s perceptions and do not reflect the true nature of the objects themselves. Emotional expressions and natural laws are also significant concepts, but they do not encapsulate Galileo's idea of what fundamentally defines the essence of reality. Primary qualities serve as the foundational basis for a scientific understanding of the universe, making them pivotal in the context of Galileo's work.