It is easy to suppose that only such symbols are complex as contain names of objects, and that accordingly “(x,φ). φx” or “(∃x,y). x R y” 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). x R y”? Can we put “not” before a name?
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