When the arguments for and against courses of action are asses-sed, it is important to remember that the choice has to be made from the available alternatives. All of them might be criticized for their imperfections, as might the status quo. Unless one of the options is perfect, the imperfections of the others are insufficient grounds for rejection. The fallacy of unobtainable perfection is committed when lack of perfection is urged as a basis for reject-ion, even though none of the alternatives is perfect either.
We should ban the generation of nuclear power because it can never be made completely safe.
(Also coal, oil and hydro-electric, all of which kill people every year in production and use. The question should be whether nuclear power would be better or worse than they are.)
If none of the alternatives, including making no change at all, is perfect, then imperfection is not grounds for a decision between them. To the matter of that choice it is irrelevant. If used to criticize only one option, it unfairly loads the case against that choice because it could be applied to all of them.
I'm against going to the Greek islands because we cannot guarantee we would enjoy ourselves there.
(When you do find a place for which this is guaranteed, let me know.)
The fallacy is very often used to reject changes to the status quo, even though the status quo itself might not be perfect.
We must ban the new heart drug because it has been occasionally associated with neurological disorders.
(This looks all right, but what if there are presently 15,000 patients dying each year of heart disease who could be saved by the new drug? Neither is the status quo perfect.)
Television documentaries and public affairs programmes are excellent source material for the unobtainable perfection fallacy. Any new proposal of government, any government, will be subjected to detailed analysis of its imperfections. Frail widows and struggling mothers will relate to cameras the hardships which will be caused, and the audience will be left with the uneasy feeling that the government is being too hasty. Exactly the same treatment could be given to the present situation.
The fallacy haunts the polished halls of committee meetings. On every committee is one person, usually a long-serving member, whose mission in life is to hold back the tide of anarchy and destruction which change represents. He castigates every new proposal with its own imperfections.
I don't think banning cars from Park Street will prevent old people being hurt. There will still be children on roller-blades and bicycles, and shopping trolleys and baby carriages. (The question is not 'is it perfect?' The issue is whether the new proposal will cut down accidents as the status quo cuts down old people.)
While you can use the general version of this fallacy to undermine any proposals you disapprove of, it will also repay you if you take the time and trouble to learn two specialist and very clever versions of it. The first of these calls for a particular suggestion to be opposed because it does not go far enough. You show its imperfections, and suggest that something more drastic is needed. This idea, therefore, should be rejected.
I approve in principle of the proposal to have the benefits allocated by lot, rather than by my personal decision, but this will still leave many areas of patronage and influence untouched. I suggest that a much wider measure is needed, looking at the whole field, and therefore I propose that we refer this suggestion back…
(It was never seen again.)
The second variant you can use has you calling for something totally beyond the powers of those making the decision, and thus sets something they cannot do in opposition to something they can.
It's all very well to suggest stiffer penalties for cheating, Headmaster, but that will not eradicate the problem. What we need instead is to win over these boys and girls, to effect a change in their hearts and minds…
(The original proposal now exits amid a crescendo of violins.)