What do we mean by left wing or right wing? People started using the language of a political spectrum when early twentieth-century political parties began to distinguish their platforms by offering different approaches to income distribution. The Terrific Engine examines how income taxation modernized political language over the period from the 1911 election through the Second World War. David Tough controversially argues that income taxation was established by popular demand, first to replace existing taxes and then to address income inequality through equalizing social programs. And, in establishing a clear basis for party differences, income taxation made elections significantly more democratic.