“Proving statements wrong by extrapolating them to extremes is an ironic way to disprove silly beliefs.”
Ideas are often argued against by extrapolating them to serious, damaging conclusions. For instance: if you allow two men to be married, then eventually you’d have to allow polygamous marriage, then bestial marriage — these worrying endpoints, when contrasted with the originally innocuous proposition, make the original sound unreasonable. The argument is also referred to as a “slippery slope”.
The problem with a slippery slope argument is that it is only just an informal fallacy because it takes deduction too far. If A causes B, then B causes C, then by deduction A causes C — so runs the classic formulation. However, if A, B, and C are as different as the three possibilities of marriage described above, the deductive links are too tenuous for the argument to hold. The true conclusion is more likely to be some middle ground, which can be more accurately determined from some related situational precedents.
There are other problems with extrapolation; indeed, if everyone extrapolated in this way all the time, the simplest interaction would immediately become problematic. A simple coffee order in a cafe may result in a statement on the implications of the purchase and how it may benefit the local economy, but then would make the outrageous leap to consider the effects on the global economy — perhaps with notions of unfair trade and other topics uninteresting to the barista, or the purchaser’s friends, who must endure the dubious extrapolation politely. The extrapolator may even incorporate other nonsense concepts like socialism or — more idiotically — karma, in a barrage of wordy, extraneous philosophising.
Inevitably in such a situation, one of the hitherto patient friends would soon break and comment on how the purchaser should “lighten up” and then extrapolate and claim the purchaser’s views will lead to enviro-nazism and fanaticism. The ineluctable conclusion would be a bloody battle, using coffee cups smashed on the edges of tables as weapons. Invariably, a stray gouged-out eye here, or an arterial spurt of blood there, would cause a disruption to the neighbouring table, forcing them to take up arms, wielding teaspoons and hardened biscotti, as they too follow the slippery slope towards mass carnage, closing with inappropriate Latin acronyms as they scald the faces of their interlocutors with reasonably hot cappuccino.
The conflict would soon escalate to a war in which the enamel weapons have been traded in for real guns. News reporters, if they hadn’t already succumbed to stroke and aneurysm from the sensationalism in this world, would soon report on this horrific global, bloody battle, now disrupting the very world economy whose imperfections were first critiqued so innocently at an ANU coffee shop. What began as a simple extrapolation of an assertion, ends in an example of the same unverifiable, hypothetical consequences redolent of the speculative deductions made in everything from climate modelling, to economic forecasts and even Kantian ethics.
Ideally, people would not wantonly extrapolate all the time and instead approach reasonable compromises. Such reconciliations, unfortunately, are not always possible. Some sentiments, for instance yes/no statements, overextended claims to truth, or blind religious beliefs, have no middle ground; and some of these have no real world precedents to examine either. In such cases deduction, ridiculous or not, serves as a valid criticism of these ridiculous asseverations.
Q.E.D.