The Theórica’s commercial and industrial goal was hegemonic in Spain during the first half of the eighteenth century, in tune with prevailing ideas in the rest of Europe. During this time the book marked ways of thinking about how the structural problem faced by Spain due to its “lack of trade” could be solved, and from 1740 onwards it became a key text, thanks to the two re-editions in 1742 and in 1757. The work was especially influential in the three areas of taxation, trade and development strategies. However, after around 1760 its influence waned due to the prevalence of doctrines in favour of prioritising agriculture. In spite of this, its proposals for taxation, support for the role of trade, which was partially open to free trade initiatives, and criticism of companies with state privileges meant that the work retained its relevance in this predominantly agrarian context. Its pro-manufacturing stance, which was largely detached from Ancien Regime rigidity and privileges, also survived among major authors and in specific fields. This chapter therefore underlines the argument that there was not just one interpretation of the Theórica but many, and that they were wide-ranging and even contradictory.