As intriguing today as when it was first published, Hume's An Enquiry Concerning Human Understanding is a fascinating exploration into the nature of human knowledge. Using billiard balls, candles, and other colorful examples, Hume conveys the core of his empiricism - that true knowledge can be gained only through sensory experience.
No other philosopher has been at the forefront of the mind than David Hume: physics, psychology, neuroscience - connections to Hume are everywhere. Here is the book that Immanuel Kant confessed to have awoken him from his "dogmatic slumber".