Slighting remark (not really an objection):  The Positivists themselves never achieved a formulation of the Verification principle that satisfied even them; they could never get it to fit just the strings of words they wanted it to fit.  As Hempel records, every precise formulation proved to be too strong or too weak in one respect or another.  There is a methodological problem as well: To test proposed formulations, the Positivists had to appeal to clear cases of both kinds, i.e., of meaningful strings of words and meaningless strings.  But this assumes already that there are strings of words that are literally meaningless even though they are grammatically well-formed and composed of perfectly meaningful words; and that is, when you think about it, a very bold and contentious claim.

Objection 1.  Wittgenstein would complain that the Verification theory is yet another monolithic attempt to get at the "essence" of language, and all such attempts are doomed to failure.  But in particular and less dogmatically, the theory applies only to what the Positivists called descriptive, fact-stating language.  But descriptive or fact-stating language is only one kind of language; we also ask questions, give orders, write poems, tell jokes, perform ceremonies of various kinds, etc.  Presumably an adequate theory of meaning should apply to all these uses of language, since they are all meaningful uses of language in any ordinary sense of the term; but it is hard to see how the Verification theory could be extended to cover them.
    Reply: The Positivists acknowledged that they were addressing meaning only in a restricted sense; they called it "cognitive" meaning.  To be "cognitively" meaningful is roughly to be a statement of fact.  Questions, commands, and lines of poetry are not fact-stating or descriptive in that sense, even though they have important linguistic functions and are "meaningful" in the ordinary sense as opposed to gibberish.
    The restriction to "cognitive" meaning was fine for the Positivists' larger metaphysical and anti-metaphysical purposes, but from our point of view, the elucidation of linguistic meaning generally, it is damaging.  A theory of meaning in our sense is charged with explaining all the meaning facts, not just those pertaining to fact-stating language.
    Second reply (Wessell-Howe):  Perhaps the nondeclaratives can be paraphrased as declaratives, and the Verification principle then applied to the paraphrases.  For example, "Will mother eat the oyster?" might be paraphrased as "I want you to tell me whether mother will eat the oyster."
    Third reply:  Perhaps the nondeclaratives can be let in in virtue of their syntactic connections to the corresponding declaratives; e.g., "Will mother eat the oyster?" and "Mother, eat the oyster!" mean what they do because of their close grammatical relation to the verifiable "Mother will eat the oyster."

Objection 2.  As noted above, the Positivists were working with admittedly preconceived ideas of which strings of words are meaningful and which are not, trying to rule out the intuitively meaningless ones and to rule in the obviously meaningful ones.  But it is not only the Positivists that had preconceived ideas about which strings of words are meaningful.  Suppose we look at a given string of words, and ask whether or not it is verifiable and if so what would verify it.  In order to do that, we already have to know what the sentence says; how could we know whether it was verifiable unless we knew what it says?
To determine how to verify the presence of a virus, say, we must know what viruses are and where, in general, they are to be found; thus it seems we must understand talk of viruses in order to verify statements about viruses, rather than vice versa.  But if we already know what our sentence says, then there is something that it says.  And to that extent, it already is meaningful.  Thus, the question of verifiability and verification conditions is conceptually posterior to knowing what the sentence means; it seems we have to know what a sentence means in order to know how to verify it.   But that is just the opposite of what the Verification theory says.
    A related point is that there is a glaring difference between the sentences that the Positivists wanted to rule out as meaningless ("Everything has just doubled in size," "The entire physical universe came into existence just five minutes ago," etc.) and paradigm cases of meaningless strings, gibberish or word salad of the sort illustrated in class ("umph glorch glumph," or for that matter "Good of off primly the a the the why").  Surely the former strings are not meaningless in the same drastic and obvious way as the latter.  Whatever may be wrong with them from an epistemological point of view, they are not mere gibberish.
    Reply: The Verificationist must come up with some difference between the two types of string, without admitting that strings of the first type are meaningful after all.  Here is a possible move.  Strings of the first type are made of regular English words and because they are grammatical from a superficially syntactic point of view, there is a kind of illusion of understanding.  Since these are the kinds of strings of words that often do say and mean something, they produce in us a feeling of familiarity.  We have the feeling that we know what they say.  And in a weak sense we do:  We can parse them grammatically, and we understand each of the words that occur in them.  But it does not follow that these strings of words do, in fact, mean anything as wholes.

Objection 3.  The Verification theory leads to highly controversial metaphysics.  Recall that a verification condition is a set of experiences.  The Positivists meant such verifying experiences to be described in a uniform kind of language called an "observation language."  Suppose our "observation language" restricts itself to the vocabulary of subjective sense-impressions, as in "I now seem to see a pink rabbit-shaped thing in front of me."  Then it follows from Verificationism that any meaningful statement I succeed in making can ultimately only be about my own sense-impressions; if solipsism is false, I cannot meaningfully say that it is.  And neither can anyone else.
    Even if instead we loosen our notion of "observation" and include what Hempel called the "directly observable characteristics" of ordinary objects, it remains true that Verificationism collapses a sentence's meaning into the type of observational evidence we can have for that sentence, without remainder.  For example, as we saw, we are driven to a grotesquely revisionist view about scientific objects  the instrumentalist view that scientific statements about electrons, memory traces, other galaxies and the like are merely abbreviations of complex sets of statements about our own laboratory data.  What is the verification condition of a sentence about an electron?  Of course it is something macroscopic, something about meter readings or vapor trails in a cloud chamber or scattering patterns on a cathode ray tube or something of the sort.  It is observable with the naked eye in the here and now.  Are we really to believe that when we talk about subatomic particles we are not really talking about little particles -- particles so small that they cannot be observed -- but instead about meter readings, vapor trails, and the like?  (The Positivists themselves did not consider this instrumentalism grotesque, but thought it importantly true; I think it is grotesque.)
    We also saw that when we turn to questions about the human mind, we find that a very strong version of behaviorism falls right out:  Statements about people's minds are merely abbreviations of statements about those people's overt behavior.  For the only sort of observational evidence I ever have regarding your innermost thoughts and feelings is the behavior I see and hear you engaging in.  If one is a Verificationist, philosophy of mind is over and done with.
    Possibly one or more of the foregoing and to me unappetizing theories are true.  Perhaps they are all true.  My point here is just that our theory of linguistic meaning should not show in one step that they are.  Metaphysics should not be settled by a theory of language, for language is just a late adaptation found in one primate species.  (Perhaps it is not even an adaptation, but a pleiotropism.)

Objection 4.  Any version of the Verification principle must presuppose an "observation language" in which experiences are described; hence it must countenance a firm distinction between "observational" and (correlatively) "theoretical" terms.  As I mentioned, some of the Positivists restricted their observation language to statements about people's private, subjective sense-impressions.  But that did not serve for purposes of intersubjectively checkable science, so most Positivists joined Hempel in appealing to the "directly observable characteristics" of ordinary objects.  There are two problems here:  First, the notion of "direct observation" is a vexed one, and seems totally technology-relative and interest- or project-relative as well.  Is a visual observation "direct" when you are wearing eyeglasses?  How about if you are using a magnifying glass?  How about through a microscope, at this or that degree of magnification?  How about through an electron microscope?
    Second, "observations," and statements couched in "observation language," are theory-laden at least to a degree; what counts as an observation and what counts as observed and how a "datum" is described are all determined in part by the very theories that are in question.
    Both these problems are knotty issues in the philosophy of science; I merely mention them here.   But they help to set up a much deeper objection to Verificationism.  That objection began to surface in class; I'll expand it here.

Objection 5.  Following Pierre Duhem, W.V. Quine argued that no individual sentence has a distinctive verification condition, except relative to a mass of background theory against which "observational" testing takes place.  This will take some explaining.
    There is a naïve idea that many people have about science.  It is that one puts forward a scientific hypothesis and then tests the hypothesis by doing an experiment, and the experiment shows, all by itself, whether the hypothesis is correct.  Duhem pointed out that in the history of the universe there has never been an experiment that could singlehandedly verify or falsify an hypothesis.  The reason is that there are always too many auxiliary assumptions that have to be made to bring the hypothesis into contact with the experimental apparatus.  Hypotheses do sometimes get disconfirmed, outright refuted if you like, but only because the scientists involved are holding certain other assumptions fixed, assumptions that are disputable and may even be quite wrong.  Suppose we are doing an astronomical experiment, and we are verifying and refuting things by making observations through complicated telescopes.  In using such telescopes, the astronomers are assuming virtually all of optical theory, and countless other things besides.
    Surprisingly, Duhem's point holds in everyday life as well.  Take any good ordinary sentence about a physical object, such as "There is a chair at the head of the table."  What is its verification condition?  A first thing to notice is that "the" set of experiences that would confirm that sentence is in a way conditional, on one's hypothetical vantage point.  We might try something like this: If you walk into the room from the direction of this door here, you will have an experience as of a chair at the head of the table.  But even that depends.  It depends on whether you have your eyes open, and it depends on whether your sensory apparatus is functioning properly, and it depends on whether the lights are on, and....  These qualifications do not foreseeably come to an end.  If we try to build in the appropriate hedges ("If you walk into the room..., and you have your eyes open, and your sensory apparatus is functioning...,..."), more qualifications crop up:  Are you walking forward rather than backing into the room?  Has something been interposed between you and the chair?  Has the chair been camouflaged?  Has it been rendered invisible by Martians?  Has your brain been altered by a freakish burst of Q-radiation from the sky?  We can go on like this for days.
    The moral is that what we take to be "the" verification condition for a given empirical statement presupposes a massive background of default auxiliary assumptions.  Those assumptions are perfectly reasonable, and it is no accident that we make them.  But a particular "verification condition" is associated with a given sentence only if we choose to rely on such assumptions, almost any of which may fail.  Intrinsically, the sentence has no determinate verification condition.  And that is (to say the least) an embarrassment for a theory that identifies a sentence's meaning with that sentence's verification condition.