Hand-waving (with various spellings) is a pejorative label for attempting to be seen as effective – in word, reasoning, or deed – while actually doing nothing effective or substantial. It is most often applied to debate techniques that involve fallacies, misdirection and the glossing over of details. It is also used academically to indicate unproven claims and skipped steps in proofs (sometimes intentionally, especially in instructional materials), with some specific meanings in particular fields, including literary criticism and speculative fiction, mathematics and logic, and science and engineering. The term can additionally be used in work situations, when attempts are made to display productivity or assure accountability without actually resulting in them. The term can also be used as a self-admission of, and suggestion to defer discussion about, an allegedly unimportant weakness in one's own argument's evidence, to forestall an opponent dwelling on it. In debate competition, certain cases of this form of hand-waving may be explicitly permitted.
Hand-waving is an idiomatic metaphor, derived in part from the use of excessive gesticulation, perceived as unproductive, distracting or nervous, in communication or other effort. The term also evokes the sleight-of-hand distraction techniques of stage magic, and suggests that the speaker or writer seems to believe that if they, figuratively speaking, simply wave their hands just so that no one will notice or speak up about the holes in the reasoning. This implication of misleading intent has been reinforced by the pop-culture influence of the Star Wars franchise, in which mystically powerful hand-waving is fictionally used for mind control, and some uses of the term in public discourse are explicit Star Wars references.
Actual hand-waving motions may be used either by a speaker to indicate a desire to avoid going into details, or by critics to indicate that they believe the proponent of an argument is engaging in a verbal hand-wave inappropriately.
Spelling and history
The spelling of the compound varies (both with regard to this idiom and the everyday human communication gesture of waving). While hand-waving is the most common spelling of the unitary present participle and gerund in this usage, and hand-wave of the simple present verb, hand wave dominates as the noun-phrase form. Handwaving and handwave may be preferred in some circles, and are well attested. "Hand waving" is mostly used otherwise, e.g. "she had one hand waving, the other on the rail", but is found in some dictionaries in this form. A more arch, mock-antiquarian construction is waving of [the] hands. Superlative constructions such as "vigorous hand-waving", "waved their hand[s] furiously", "lots of waving of hands", etc., are used to imply that the hand-waver lacks confidence in the information being conveyed, cannot convincingly express or defend the core of the argument being advanced. The descriptive epithet hand-waver has been applied to those engaging in hand-waving, but is not common. The opposite of hand-waving is sometimes called nose-following in mathematics (see below).
However it is spelled, the expression is also used the original literal meaning of gesturing in a greeting, departing, excited, or attention-seeking manner by waving the hands, as in "friendly were the hand-waving crowds ..." (— Sinclair Lewis), which dates to the mid-17th century as a hyphenated verb and the early 19th century United States as a fully compounded verb. It is unclear when the figurative usage arose. The Oxford Dictionary of English lists it as "extended use", and it appears primarily in modern American dictionaries, some of which label it "informal".
In debate, generally
Handwaving is frequently used in low-quality debate, including political campaigning and commentary, issue-based advocacy, advertising and public relations, tabloid journalism, opinion pieces, Internet memes, and informal discussion and writing. If the opponent in a debate or commentator on an argument alleges hand-waving, it suggests the proponent of the argument, position or message has engaged in one or more fallacies of logic, usually informal, and/or glossed over non-trivial details, and is attempting to wave away challenges and deflect questions, as if swatting at flies. The distraction inherent in the sense of the term has become a key part of the meaning. The fallacies in question vary, but often include one of the many variants of argument to emotion, and in political discourse frequently involve unjustified assignment or transference of blame. Hand-waving is not itself a fallacy; the proponent's argument may incidentally be correct despite their failure to properly support it. A tertiary meaning refers to use of poorly-reasoned arguments specifically to impress or persuade.
The New Hacker's Dictionary (a.k.a. The Jargon File) observes:
If someone starts a sentence with "Clearly..." or "Obviously..." or "It is self-evident that...", it is a good bet he is about to handwave (alternatively, use of these constructions in a sarcastic tone before a paraphrase of someone else's argument suggests that it is a handwave). The theory behind this term is that if you wave your hands at the right moment, the listener may be sufficiently distracted to not notice that what you have said is bogus [i.e., incorrect]. Failing that, if a listener does object, you might try to dismiss the objection with a wave of your hand.
The implication that hand-waving is done with the specific intent to mislead has long been attached to the term, due to the use of literal waving of a hand – either natural-looking or showy, but never desperate – by illusionists to distract audiences and misdirect their attention from the mechanisms of the sleight-of-hand, gimmicked props or other trick being used in the performance. This meaning has become reinforced in recent decades by the influence of Star Wars (1977) and its sequels, in which the fictional Jedi mind trick involves a subtle hand wave with mystical powers – that only work on the weak-minded – to disguise reality and compel compliance. Consequently, there is an implication in current usage that a hand-waver may be craftily intending to deceive, and has a low opinion of the intelligence of the opponent or (especially) an audience or the general public. The labels "Jedi hand wave" and "Jedi mind trick" themselves are sometimes applied, in a tongue-in-cheek way, to this manipulation technique in public discourse; US Congressman Luke Messer (Republican–Indiana) use of it in reference to President Barack Obama's 2016 State of the Union address generated headlines.
In an unplanned debate or presentation, an off-the-cuff essay, or an informal discussion, the proponent may have little or no time for preparation. Participants in such exchanges may use the term in reference to their own arguments, in the same sense as an author admitting a minor plot flaw (see below). When the proponents use the term, they are conceding that they know an ancillary point of or intermediate step in their arguments is poorly supported; they are suggesting that such details aren't important and do not affect their key arguments or conclusions, and that the hand-waved details should be excluded from current consideration. Examples include when they believe a statement is true but cannot prove it at that time, and when the sources upon which they are relying conflict in minor ways: "I'm hand-waving over the exact statistics here, but they all show at least a 20% increase, so let's move on".
In formal debate competition, certain forms of hand-waving may sometimes be explicitly permitted. In policy debate, the concept of fiat allows a team to pursue a line a reasoning based on a scenario that is not presently true, if a judge is satisfied that the case has been that it could become true.
In literary criticism
By extension, handwaving is used in literary, film and other media criticism of speculative fiction to refer to a plot device (e.g., a scientific discovery, a political development, or rules governing the behavior of a fictional creature) that is left unexplained or sloppily explained because it is convenient to the story, with the implication that the writer is aware of the logical weakness but hopes the audience will not notice or will suspend disbelief regarding such a macguffin, deus ex machina, continuity error or plot hole.
The fictional material "handwavium" (a.k.a. "unobtainium", among other humorous names) is sometimes referred to in situations where the plot requires access to a substance of great value and properties that cannot be explained by real-world science, but is convenient to solving, or central to creating, a problem for the characters in the story. Perhaps the best known example is the spice melange, a fictional drug with supernatural properties, in Frank Herbert's far-future science-fantasy epic, Dune.
Hand-waving has come to be used in role-playing games to describe actions and conversations that are quickly glossed over, rather than acted out in full according to the rules. This may be done to keep from bogging down the play of the game with time-consuming but minor details.
In mathematics (and thus some formal logic, philosophy, and theoretical science)
In mathematics, and theory-dominated disciplines in which mathematics plays a major role, hand-waving refers to the following behavior, which is expected from students (and can be used to advance instruction), but which is considered intolerable and inexcusable among professionals. In this context, hand-waving is not merely a pedagogical paradigm or rhetorical device. Rather, it represents a formal logical fallacy, wherein a conclusion (which may be uncontested) is ascribed to follow from a demonstrably unreliable source of argumentation. The important distinction from the benign and informal interpretation of "proof by hand-waving" in science and engineering (see below), is that the validity or falsehood of any proposals or hypotheses, though asserted and claimed to be true, are never called into question; instead, a diagnosis of mathematical hand-waving is effectively a professional attack, intended to undermine the legitimacy of a speaker who has attempted to assert a proposition, without necessarily having the power to prove it, at least not without appealing to authority or consulting notes or references.
In general, working mathematicians are implicitly more receptive to legitimate contributors than to any source of equivocation, and consequently consider themselves to be more rewarded by a constructive denunciation than by any competent and correct but illegitimate or indefensible instruction. Especially when expositing a newly discovered theorem, mathematicians must be able to validate any proposition that is explicitly attested in the course of their argumentation. In the practical event that any of their assertions are challenged (in good faith) by a member of their audience, the theorists' professional qualifications entail that they be fully prepared to achieve such validity up to any degree of absolute certainty, including rigorous demonstration by formal mathematical proof. This is important because, should a speaker apparently or demonstrably fail to achieve this standard, anyone in the audience having a sufficiently superior expertise to provide the needed demonstration can often be expected to mercilessly upstage this person on the spot; and such an attack is likely to be deemed warranted in the eyes of an audience which, generally speaking, does not like to be hand-waved at. Moreover, the objector in such a case could receive some measure credit for the theorem the hand-waver presented.
The opposite of hand-waving in mathematics and related fields is sometimes called nose-following,[clarification needed] a behavior which, although usually counter-productive, is characteristic of logical veracity. The reason why behaviors such as hand-waving and nose-following, and the particular ways that these are identified and responded to, tend to be more profound in mathematics than in other disciplines, seems to be suggested by the following quote of G. H. Hardy. "[A mathematician's] subject is the most curious of all—there is none in which truth plays such odd pranks. It has the most elaborate and the most fascinating technique, and gives unrivalled openings for the display of sheer professional skill."
In applied science and engineering
Hand-waving arguments in engineering and other applied sciences often include order-of-magnitude estimates and dimensional analysis, especially in the use of Fermi problems in physics and engineering education. However, competent, well-intentioned researchers and professors also rely on explicitly declared hand-waving when, given a limited time, a large result must be shown and minor technical details cannot be given much attention—e.g., "it can be shown that z is an even number", as an intermediary step in reaching a conclusion.
Back-of-the-envelope calculations are approximate ways to get an answer by over-simplification, and are comparable to hand-waving in this sense.
Hand-waving has been used to describe work-related situations where productivity is seemingly displayed but deliverables are not produced, especially intentional engagement in busy work or pretend-work, vague claims of overwork or complications, impenetrably buzzword-laden rationalizations for delays or otherwise poor performance, and plausible-sounding but weak excuse-making and attention-deflecting tactics. In employment situations, as in political discourse, a hand-waving effort may seek to shift blame to other parties.
Another use is in reference to fiscal problems, such as an inability to adequately explain accounting discrepancies or an avoidance of accountability for missing funds.
- "hand wave". Dictionary.com. 2016. Cites the Random House Dictionary and The Dictionary of American Slang 4th ed.
- Raymond, Eric S.; Steele, Guy L., eds. (1996). "handwave". The New Hacker's Dictionary (3rd ed.). MIT Press. ISBN 0-262-68092-0. Online edition: "The Jargon File". 4.4.7. Homepage mentions a ver. 4.4.8, but the text of the work says 4.4.7.
- Examples in the political press of "Jedi hand wave": http://townhall.com/columnists/kurtschlichter/2015/11/23/more-lame-virtue-signaling-from-president-faily-mcworsethancarter-n2082900/page/full ;
and in the sports press of "Jedi mind trick": http://www.cbssports.com/nfl/eye-on-football/25449738/one-bronco-thinks-roethlisbergers-injury-is-a-jedi-mind-trick .
- Usage patterns are easily observable with Google and other search engines, which also reveal the difficulty of excluding false positives from various particular search terms.
- "hand-wave". Oxford Dictionaries Online (British and World English ed.). Oxford University Press. 2015. Retrieved January 26, 2015. This is an online edition of Oxford Dictionary of English with additional material.
- "handwave". Oxford Dictionaries Online. American English. Oxford University Press. 2015. Retrieved January 26, 2015. This is an online edition of the New Oxford American Dictionary.
- "hand-waving". Oxford Dictionaries Online. American English. 2015. Retrieved January 26, 2015.
- "Gus Wiseman's answer to What do mathematicians mean by "hand-waving" and why is it important?".[self-published source?]
- "Hugh O'Byrne's answer to What do mathematicians mean by "hand-waving" and why is it important?".[self-published source?]
- "Polycategories via pseudo-distributive laws".
- G. H. Hardy (1940). "A Mathematician's Apology".