How did Epicurus explain human knowledge through the senses?

Epicurus developed an explicitly empiricist account of knowledge, grounding his philosophy in the belief that all sensations and representations are true and serve as the primary criteria for truth.12

In his work On the Criterion, or Canon, Epicurus established that human knowledge is derived from the following:

• Sensations: Epicurus assigned truth to sensation, viewing it as the foundation of all knowledge. He rejected the deductive approach of earlier thinkers like Democritus, who considered sensory information to be spurious, and instead reduced the intellect to sensory experience.2
• Concepts (prolēpsis): These are mental residues or "recollections" of what has been frequently presented to the senses from the external world. They serve as a background for understanding terms and concepts.2
• Mental Images: Epicurus’s psychology posited that thought occurs through the perception of images—films of atoms that continuously emanate from objects and reach the mind (psychē) through the pores.2

While sensations are inherently true, error becomes possible when the mind adds judgment to these perceptions, particularly when tying terms into propositions or speculating about objects beyond direct experience. To navigate this, Epicurus used sensations as "signs" to conjecture about what does not appear, maintaining a consistent empirical framework.21