In this message, American geneticist and artificial intelligence (AI) trailblazer Joshua Lederberg (1925–2008) muses about the difference between human and machine learning, describing how his thinking on the matter has changed with experience. Joshua Lederberg helped develop DENDRAL, the first “expert system,” or computer program that simulates the judgement of human experts on a topic. DENDRAL analyzed chemicals as proficiently as human chemists.