This article seeks to recover a history of ideas about the role of signs in the development of mind that connects Vygotsky to major traditions in Enlightenment language studies. It offers historical perspectives on ideas about thinking and speaking that shed light on the scope and trajectory of Vygotsky’s conception of signs as psychological tools. The Soviet thinker was schooled in German humanities, philology and philosophy. He was also indebted to thinkers of the European Enlightenment, especially Bacon, Locke and Condillac, for ideas about the role of signs in the formation of mind. I explain how ideas about the relationship between words and ideas set down by Locke were taken up and extended by Condillac in a seminal theory of knowledge. According to Condillac, signs play a key role in the development of mind. Later, Herder and von Humboldt built on Condillac’s ideas. Herder suggested that individual psychologies are shaped in concrete, historical circumstances, and pictured an organizing, creative f...