Aristotle believed that the physical world was made up of both matter, which can be sensed, and form/essence, which cannot be sensed. He categorized knowledge into different types based on their objects and the certainty with which they could be known. Aristotle was an empiricist who believed that knowledge comes from sense experience and inductive reasoning, though our senses are flawed. Unlike Plato, he believed that form is inherent in physical objects, not separate from them.