Tuple を使うと、アリストレス論理学の Categorical proposition だけで、RDBあるいは Datalog の方法を使うと、述語論理の論理式をシミュレートできるが、

But this derivation (上でシミュレーションと読んでいるもの）fails, as Russell points out, because the selected
couples tacitly exhibit, in the order of their presentation, the very relation they are called on to define.
The notion of relation cannot be reduced to that of class; it must be treated as primary.

という、Skidelsky “Ernst Cassirer” 2008, p.60 の記述は、Russell, The principles of mathematics, Chap. IX,
§98. A relation is not a class of couples を指している。