“If the length of the one is L the length of the other is L”. This is a Form of various props. but not itself a prop. But we could say: “If ˇLet us put ‘L’ instead of ‘length’: we put ‘L’ then they have the same L.
    But it makes sense to say: “Let us consider props. of the form “if A has the length L so has B”.”

55