[Old jottings from my journal.] Lenin’s Materialism and Empirio-Criticism, from the selections I’ve read so far, is sensible. (That isn’t the academic consensus, but what do you expect from philosophers? He’s a Commie, after all.) Here’s one of his briefer summaries of George Berkeley’s thought: “Let us regard the external world, nature, as a ‘combination of sensations’ evoked in our mind by a deity. Acknowledge this and give up searching for the ‘ground’ of these sensations outside the mind, outside men, and I will acknowledge within the framework of my idealist theory of knowledge all natural science and all the importance and authenticity of its deduction…” This view is essentially that of the logical positivists, of Carnap and Ayer and the rest. They were basically idealists, albeit of a special kind. Like them, Berkeley considered realism and materialism to be little more than nonsense—although the positivists’ reasons for saying so were different, namely that metaphysical statements cannot be empirically verified. So they also considered Berkeleyan idealism, which makes metaphysical claims, nonsensical, while nonetheless implicitly adhering to it far more closely than to realism. For they rejected all talk of mind-independent matter. Within a certain linguistic framework, argued Carnap, it makes sense to talk about independently existing objects, e.g. the frameworks of natural science and common sense; but it’s meaningless to ask, from a position external to these frameworks, whether there “really” exist things in themselves. To do so is effectively to question the reality of the frameworks themselves, which doesn’t make sense because frameworks aren’t the sort of things that can be “real.” In the framework of science it’s useful to talk about the reality of electrons, and in the framework of ordinary language it’s useful to talk about the reality of tables, and that’s all that can be said. So the difference between the positivists and Berkeley is that the former consider the question of things in themselves meaningless, while the latter considers the realist/materialist answer meaningless. But then they both come out on the side of idealism, since all they recognize are sense-data. (The positivists consider objects and the world to be logical constructions out of sense-data. Again, Berkeley.) You see: metaphysics can’t be avoided, even by those who think they’re avoiding it. And Lenin is right that Ernst Mach and his disciples are derivative of Berkeley.
Ironically, (some of) the positivists were, in a way, even more idealistic than Berkeley. For Berkeley thought that the existence of “objects” even when we’re not perceiving them is guaranteed by the existence of God, who perceives them at all times. But the positivists rejected the question entirely, which, given their other doctrines, effectively meant that reality consists only of sense-data and “logical constructions.” It’s a very paradoxical, i.e. stupid, doctrine. And it makes natural science a mystery, and (ironically!) a sort of delusion. For science does postulate things in themselves.
I simply fail to understand how a phenomenalist, someone like Ernst Mach or Ayer and Carnap in their early years, can accept scientific explanations literally. How can he accept that the nervous system constructs experience? The nervous system, like all external things, is mind-independent! If only sensations and logical constructions out of them exist, then there is no nervous system (independent of our sensations)! And so consciousness and sense-data, being effectively the only things that exist, become a permanent mystery, as does science itself. Is it possible for thinkers to be so confused?? Lenin shares my befuddlement. “…Sensation, then,” he paraphrases, “exists without ‘substance,’ i.e., thought exists without brain! Are there really philosophers capable of defending this brainless philosophy? There are!”
I emailed Chomsky about this. He answered: “Carnap wasn’t a phenomenalist in the usual sense. In his Logische Aufbau der Welt he did take sense data as a basis for his constructions, but that is because it seemed to him to work, as opposed to taking physical objects. And he accepted scientific explanations. There’s no inconsistency. We can believe, with Russell, that the most trustworthy evidence we have is our own immediate experience and that science is the organized effort to make sense out of it, and still regard the whole edifice of science, including postulation of the nervous system, as the best explanation, with no inconsistency.” Obviously the last sentence is right. But if we don’t countenance the existence of mind-independent matter, surely we can’t accept scientific explanations. From everything I’ve read by and about them, the logical positivists—at least, most of them—rejected not only the existence of theoretical entities but even the meaningfulness of the statement that matter exists independently of its being perceived. (Thus, Ayer said that “The chair exists when I’m not looking at it” means only that I would have certain sense-impressions if I looked in ‘its’ direction. (Again, similar to Berkeley.)) But science is, surely, committed to the mind-independence of matter, or scientific realism. So it seems that Ayer and others, if my characterization of them is correct, can’t consistently believe in the literal truth of scientific hypotheses.
I sent that to Chomsky. He wrote, “That’s Ayer, a vulgarization of logical positivism. Carnap wouldn’t have agreed. He was a physicist – as many of the Vienna Circle were – and a large part of his goal was to provide means for physics to carry out its work more clearly and successfully.” Yes, I know, which is what confuses me. Carnap was obviously more sophisticated and subtle than Ayer, but I can’t agree with him that all ontological questions are meaningless. Questions about [the existence of] numbers, classes, properties and propositions are, but not questions about ordinary everyday objects and theoretical entities like atoms, since these are supposed by most physicists themselves to have real existence in spacetime. More generally, there either is (mind-independent) matter or there isn’t. That can’t be a pseudo-question, because common sense and science are both committed to the position that there is matter. Period. (Nothing about “linguistic frameworks” here.) Which means it’s a substantive position. Carnap wanted to navigate between realism and instrumentalism (anti-realism, a kind of idealism), but that seems impossible to do. Was he some sort of “structural realist”? Did he reject realism about theoretical entities but accept it vis-à-vis the mathematical structures of physical theories? Perhaps. But then, if so, he was an anti-realist in a sense—and a realist in another—which means he took a “metaphysical” position.
I’m always suspicious of philosophies that can’t be stated in plain English. All this talk about “linguistic frameworks” and this refusal to be pinned down to one position, at times adopting the language of realism, at others the language of idealism, and at others saying that the whole issue is misguided—makes me suspicious.
 One problem: solipsism. If there are no mind-independent things, then there are no people besides me. Berkeley at least had a theory to address this problem.