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According to John Loche, the idea of solidity is a primary idea. According to him, solidity is a primary idea since it cannot be lost. For instance, if we divide wheat into different particles, its solidity will still remain thus making it a primary idea.
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Locke goes further is defines what he means by solidity. In physics, solid is a physical state of matter different from liquid and gases. The only thing which Locke uses to define solidity in this case is the ability to displace other objects in an area and occupying it. Solid objects in this case may lose their color by they will still have a shape. Moreover, if one views such an object through say a microscope may seen more colors than those seen without the microscope.