Blanshard next summarizes his critique. But what does “necessity” mean?
“It means, replies the empiricist, only that certain parts have been presented together with such unfailing regularity that we have become unable to dissociate them. … Formalism we have found more plausible. It admits the element of necessity that empiricism denies; its peculiarity is that it confines the necessity within certain highly general forms. … As for symbolic logic, we found it [ ] less helpful than the older logic, primarily because with its decision to ignore intension, it had abandoned interest in necessity. Of its three principal ways of conceiving implication, material, formal, and strict, we recognized an advance over the others, but could find in none of them a definition that would cover, even approximately, the necessity actually used in inference and understanding. We are left with this conclusions; necessity is not a habit, induced in us by an inexplicable regularity of presentation. Necessity is not a form or skeleton which, while sustaining the fleshy matter of the world, is sharply distinct from it” (397-8).
Blanshard’s use of “empiricist” clearly includes Hume, Mill, and other later philosophers. He references Hume and Mill. He doesn’t reference Locke, and I believe it would be unfair to include John Locke, the leading empiricist, among those whom Blanshard critiques. Locke wrote about habit and ideas by association (in ECHU), but he is not mentioned in The Nature of Thought, Volume 2, nor did he reduce all inference to habit like Hume did.