Do we have in the following, I wonder, an intended criticism of Parmenides?
When uttered just by itself a verb is a name and signifies something--the speaker arrests his thought and the hearer pauses--but it does not yet signify whether it is or not. For not even 'to be' or 'not to be' is a sign of the actual thing (nor if you say simply 'that which is'); for by itself it is nothing, but it additionally signifies some combination, which cannot be thought of without the components.The translation is Ackrill's, and of course it is De Int 16b19-25. Ackrill remarks: "Though Aristotle uses the infinitives 'to be' and 'not to be', these must--if the sentence is to have any relevance to what went before--be taken as stand-ins for indicative forms, 'is', 'is not', 'was', &c." So Aristotle's claim is that 'is' (esti) as much as 'is not' (ouk esti) fails, on its own, to express a thought.
Au)ta\ me\n ou)=n kaq' e(auta\ lego/mena ta\ r(h/mata o)no/mata/ e)sti kai\ shmai/nei ti—i(/sthsi ga\r o( le/gwn th\n dia/noian, kai\ a)kou/saj h)re/mhsen—a)ll' ei) e)/stin h)\ mh/, ou)/pw shmai/nei: ou)de\ ga\r to\ ei)=nai h)\ mh\ ei)=nai shmei=o/n e)sti tou= pra/gmatoj, ou)d ' e)a\n to\ o)\n ei)/ph|j au)to\ kaq' e(auto\ yilo/n. au)to\ me\n ga\r ou)de/n e)sti, prosshmai/nei de\ su/nqesi/n tina, h(\n a)/neu tw=n sugkeime/nwn ou)k e)/sti noh=sai.
The argument, as against Parmenides, is presumably this. Distinguish thinking from thinking of something: the latter involves a judgment. A verb on its own involves thinking merely and fails to express a judgement. It might appear to do more, only because it arrests thought. Not even the verb 'exists' is an exception. That word, like any other verb, looks to be completed, having significance about something only in combination with something else. (And now here is an old objection against monism.) You succeed in thinking ofwhat exists, then, only by combining 'exists' with another word, in which case there would be at least four things, not one, which exist (the two words, and the two things signified by those words).
Parmenides believes that he has isolated the only 'way' that is thinkable, the way of 'is' (esti). But simply saying 'is', although this is to think, is not to think of something: in fact, it is to think of nothing! Yet say something more, and your claim of monism is self-defeating. Even an assertion of absolute unity would require two words!
(On prosshmai/nei, Ackrill compares 20a13: "So 'every' and 'no' additionally signify nothing other than that the affirmation or negation is about the name taken universally." Ackrill comments: "He does not, of course, mean that 'every' has some straightforward significance and also serves to quantify the subject, but that what its presence adds to a sentence is quantification.")