What did John Locke mean by sensation and reflection?

In his An Essay Concerning Human Understanding, John Locke identified sensation and reflection as the two fundamental sources of all human ideas, rejecting the doctrine of innate ideas.12

• Sensation: This is the process by which the mind receives information from the external world through the senses. It provides the mind with simple ideas derived from sensory experiences, such as colors, sounds, tastes, and textures.123
• Reflection: This refers to the mind’s internal awareness of its own operations. It is the process by which an individual becomes conscious of their own thinking, emotions, and the act of having sensations.142

Locke argued that these two sources provide the "materials" of knowledge, which he called ideas. While sensation provides the raw sensory data, reflection allows the mind to process, combine, and compound these simple materials into complex conceptual entities. Together, these mechanisms form the basis of his empiricist epistemology, positioning the mind as an agent that discovers knowledge through experience rather than possessing it innately.1234