So, Philosophers'Imprint just published a paper on Stoic #FirstOrderLogic & #MultipleGenerality that I co-authored with SimonShogry, in which we argue that the Stoics had all it takes to accommodate multiple generality in a variable-free 1st-order logic (abstract link below)(1/6)

Still, the quoted statement has become the communis opinio (prevailing doctrine). See e.g. Wikipedia, the entry on #MultipleGenerality: "The first logical calculus capable of dealing with such inferences [i.e. with multiple generality] was Gottlob Frege's Begriffsschrift (1879)"