David Hume's An Enquiry Concerning Human Understanding was considered to be one of the most contentious works of its time. Hume's view of reasoning through experience and "sophistry and illusion" in reference to religiously inspired fantasy was extremely controversial in the 18th century.
In today's climate of science denial, Hume's work is still relevant and just as controversial. The Enquiry delves into human understanding and the physical world, highlighting just how little man understands reality, concluding that human understanding is limited to experience and instinct.
Hume's rational skepticism offers food for thought on human experience and a basis for scientific understanding aimed at liberating man from superstitious religions. His work is the first of its kind to take the focus off religion and put it on the physical world. David Hume's Enquiry Concerning Human Understanding is still considered to be one of the best introductions to the study of philosophy.