It is easy to suppose that only such symbols are complex as contain names of objects objects, & ˇthat accordingly “(∃x,φ).φx” or “(∃x,ˇR,y).xRy” must be simple. It is then natural to call the first of these the name of a form, the second the name of a relation. But in that case what is the meaning of (e.g.) “~(∃x,y).xRy”? Can we put “not” before a name?
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