More than a classic work on the history and philosophy of science, Kuhn's 1962 book is considered by many to be one of the greatest works of the 20th century. Kuhn helped change the way everyone looks at science. He argues that scientific development is not linear but runs in cycles, alternating between periods of "normal" and "extraordinary" science where breakthroughs occur. Kuhn questions the idea that science is only based on evidence; rather, it has always been based on unspoken assumptions he calls "paradigms." When an accepted paradigm is succeeded by another—often based on the promise of better scientific solutions rather than immediate solutions—a "scientific revolution" unfolds.