Explore the intriguing world of visual perception in this thought-provoking lecture by Dale Purves from Duke University. Delve into the fundamental challenges of vision and how our brains interpret the world around us. Discover why what we see doesn't always align with physical reality, using examples like the perception of line length based on orientation. Examine the underlying problem of how we can successfully navigate the world without accurately measuring it. Learn about an empirical approach to understanding vision through accumulated trial and error experiences. Investigate the process of collecting data on visual stimuli frequency and how it relates to human perception. Consider the role of reflexes as a universal strategy in vision. Gain insights into the key concept that the real-world sources of images cannot be known, and how this impacts our understanding of visual perception.