In his Essay Concerning Human Understanding, Locke argued against the concept of innate ideas. Various thinkers, including Plato and Descartes, had claimed that some ideas are within us from birth. Instead, Locke proposed that knowledge exclusively comes from experience. We can gain knowledge either through the senses (1) or through reflection on this sensory data (2).
To bring this point home, he famously wrote:
No man's knowledge here can go beyond his experience.