This article proposes a critical analysis of the thought of Jean-Baptiste Say, on his approach to the economy in general, and his position on slavery in particular. It comprises two parts. The first deals with his general approach to the economy, especially his definitions of value, capital, and equilibrium of market supply and demand (Say’s law). The second addresses a less well-known issue, that of positions adopted by Say on slavery (and on colonies), with the aim of examining their strengths and limitations. Say’s liberal followers often draw attention to his work “Say’s law” and the glorification of capital while discarding his anti-slavery theses that constitute an advocacy for the liberation of the forces of production to the service of a triumphant capitalism. JEL Codes : B12, F02, J41, J71, K33, N43, O52, P12