Go read this post on QandO wherein Billy Hollis makes a great argument by analogy. Here’s a summary, but seriously, go read it all:
Consider the following generic proposition:
“System Y is a complex system, and its destabilization would have a dramatic negative impact on society. Factor X is known to influence System Y, and the growth of Factor X is believed to destabilize System Y and even make it possibly vulnerable to catastrophic Failure Mode Z.
“Therefore, for the good of society, it’s extremely important to reduce Factor X. Everyone must make sacrifices to avoid Failure Mode Z.”
… Let’s take a look at a couple of real cases of the proposition.
First, let’s consider
System Y = global climate
Factor X = carbon dioxide
Failure Mode Z = significant global temperature rise with attendant sea level rise and other forms of extreme environmental degradation
With this particular substitution, most of those on the left would vigorously assure us that the proposition was valid. They would then tell us that, in order to reduce carbon dioxide, drastic measures are needed, even though those measures have some very undesirable side effects on various members of society.
Next, let’s consider
System Y = US or world financial system
Factor X = government spending and debt
Failure Mode Z = financial system meltdown, in which financial institutions fail en masse, and normal commerce is halted or seriously disrupted
Now, if we make this substitution and present the proposition to a typical leftist, their reaction would be quite different. They would very likely not agree that drastic measures are needed to reduce spending and debt. Based on recent arguments from the left, they would look to comparatively small changes to address any dangers, such as raising taxes on rich people, or “rooting out fraud and waste”. Such changes have been tried before, and clearly are not a long term fix, yet the left keeps insisting that they are sufficient to head off potential financial catastrophe.
Leftists would probably argue that government spending and debt isn’t what would lead to financial meltdown, but rather unethical and greedy behavior on the part of corporate leaders, bankers, and investors, combined with insufficient (rather than too much) government regulation and oversight. Consequently, they could claim — fairly, I think — that from their point of view, the second case doesn’t fit the model.
Even though this particular example may be a bit flawed, this illustrates a great way of reasoning by analogy.
Here’s a better example:
System X is comprised of so many interacting parts and is so complex that it is beyond our ability to understand it or manage it or control it.
Therefore we should not intervene in System X.
In general, liberals believe this proposition about foreign wars and interventions but not about the economy; conservatives believe this about the economy but not about foreign wars and interventions. Hence, both of them are guilty of inconsistent thinking, driven by their ideologies.