The Ricardian dynamics are based on the study of the order of cultivation when demand increases. Sraffa criticized Ricardo for having assumed that the incoming agricultural method is defined by a natural order and stressed that the law of succession of methods is based on a profitability criterion. Then, in the case of intensive cultivation, the question is whether the incoming method is indeed more productive than the one it replaces. Sraffa’s argument relies on the positivity of rent. However, there is a flaw in his reasoning and a failure of the Ricardian dynamics is possible. Post-Sraffian scholars have misunderstood that construction and have substituted a static approach for it. The critiques they address to Sraffa are better understood by returning to Ricardo and Sraffa's own methodology. Fifty years ago, mathematicians rediscovered Ricardo's approach independently and worked out a powerful algorithm inspired by it.