The sentence, "What is so rare as a day in June?" would be considered by these sources a sentence without a truth value, because it is a question as well as a line of poetry from James Russell Lowell's "The Vision of Sir Launfal." Poetry as expressive discourse is neither true nor false. As such, one would think this sentence would have no use in a purported argument such as this one: "Father's Day is a beautiful day, for, as they say, what is so rare as a day in June?"
Such an interpretation leads to inconsistency of application of the basic terms of an argument when the topic of informal fallacies arises. Here, passages with non-declarative sentences are routinely used for fallacy examples. For example, the Wikipedia entry for (fallacy of) compound question explains the question, "Are you still beating your wife?" in this manner:
Compound questions are a common feature in loaded questions such as "Are you still beating your wife?" The argument is phrased as a single question requiring a single answer, but actually involves two or more issues that cannot necessarily be accurately answered with a single response.
However as Prof. Gary N. Curtis explains in The Fallacy Files with respect to this example ...
Since a question is not an argument, simply asking a loaded question is not a fallacious argument. Rather, loaded questions are typically used to trick someone into implying something they did not intend.
The only way to determine whether an argument is present is to look at the context and intention of the locutor. ("Locutor" is a term first used by Thomas Vernon in his Philosophy of Language Primer, (University Press of America, 1980).) In particular, the context and circumstances which occasion the use of the particular utterance is essential for the identification of fallacies.
As Grice points out, the meaning of a sentence is what a speaker means when he utters the sentence--in a sense this is a narrower interpretation of Wittgenstein's observation that sentence only makes sense when a context is provided:
When does a sentence make sense? ... There was talk about [G.E.] Moore's sentence: I am here....if it were a question in a True-False questionnaire, you would clearly answer "True" or "Yes" if asked: Yes or No. W.[Wittgenstein] said; "No! No! Of course not, etc. Context determines use.
(O.K. Bouwsma, Wittgenstein Conversations 1949-1951, ed. by J.L. Craft and Ronald E. Hustwit (Indianapolis: Hackett, 1986), 15.)
When no context is provided, common sense should prevail. In many editions of Copi and Cohen's popular Introduction to Logic, we find example exercises which require the student treat a passage as an argument when no argument is present.
Consider these examples:
He that loveth not knoweth not God for God is love. --1 John 4:8
Forbear to judge, for wa are sinners all. --William Shakespeare, Henry VI, Part III, act III sc. 3 line 31.
(Irving M. Copi and Carl Cohen, Introduction to Logic, 9th ed. (New York: Macmillan,1990), 17.)
Clearly the contexts provided by the annotated references preclude the intent of providing an argument in these instances.
The presence of an argument, then, should not be concluded on the simply on basis of the sentence type but rather on the basis of the context, intent and sentence function of the passage under examination.
Consider the following passage:
The federal budget is months overdue, and it appears that the Democrats will have to give in to many of Mr Bush's spending demands, even at the expense of the domestic programmes they wanted to augment. Will voters punish the Democrats at the 2008 election for Congress's disappointing year, or will they whack the Republicans for their obstructionism?
("The Do-Nothing Congress," The Economist, 385, No. 8554 (15 December 2007), 39.)
The complex fallacy normally identified here by those who have studied logic is a complex question using the variously termed fallacy of false dichotomy, black-or-white fallacy, false dilemma, or false choice. If it is an argument, note that the conclusion is a question. The import of the question points to a disjunctive statement. The argument popularly would be considered fallacious here because, in fact, there are other possible alternatives than "punishing" or "whacking."
However, let's look at the context and intent of the passage. If, by the principle of charity, we remove the emotionally charged words in the conclusion ...
Either voters punish the Democrats because ...
Or voters whack the Republicans because ...
to mean something like "The voters will either vote Republican or Democrat," for that is the factual significance of the question, the triviality of the statement yields the implication that the passage is not so much a fallacy of complex question as it is an editor's (emotively significant) comment.
Of course, the assumptive reasons provided in the passage for voting Democratic or Republican may be challenged on the basis that there are other alternatives. But I think the safest course is to regard the comment as expressive discourse. The editor is expressing an opinion; he is not drawing a conclusion on the basis of the premise that the Democrats are under pressure to agree to President Bush's proposals. It is a factual claim not a logical claim that this pressure will cause them to vote either Republican or Democratic. The rhetoric of the passage obscures the fact that no argument is present.
Just so, however, I acknowledge that my interpretation of the quoted editorial passage from The Economist is a close and probably controversial call even upon careful study of the context of the complete article.