Jean-Baptiste Say was a French economist born in 1767, best known for his contributions to classical economics. He is famous for formulating Say's Law, which states that supply creates its own demand. This principle suggests that production is the key to economic growth, as goods produced will eventually be purchased. Say also played a significant role in promoting the ideas of Adam Smith and other classical economists. He wrote several influential works, including the "Traité d'économie politique," where he discussed the importance of entrepreneurship and the role of the entrepreneur in driving economic activity.