What is a “Straw Vulcan”?

From TV Tropes:

SpockVulcanA straw man used to show that emotion is better than logic.

It starts by having characters who think “logically” try to solve a problem. And they can't. Either they can't find any answer, or they're caught in some kind of standoff, or they're even stuck in a Logic Bomb-type loop. Once this is established, someone who uses good old human emotion comes up with a solution that the logical thinker can't. This provides An Aesop that emotion is superior and that the logical thinker shouldn't trust logic so much.

This is, of course, a broken Aesop. Fiction often gets the concept of logic wrong in a number of ways.

The most common mistake is to assume that logic and emotion are somehow naturally opposed and that employing one means you can't have the other. Excluding emotion doesn't make your reasoning logical, however, and it certainly doesn't cause your answer to be automatically true. Likewise, an emotional response doesn't preclude logical thinking — although it may prevent you from thinking in the first place — and if an emotional plan is successful, that doesn't make logic somehow wrong.

Because the author is more concerned with setting up their strawman than in handling logic correctly, they will often misuse and distort the concept to create contrived examples where what they're calling “logic” doesn't work. Common situations include:

  • The Straw Vulcan will only accept a guaranteed success. A plan that only has a chance of success is not “logical”, even if the chance is the highest possible. This is actually a well-known error in logic, called the Perfect Solution Fallacy.
  • The story assumes a “logical” plan is one where every step makes the goal visibly closer, and accepting a short-term disadvantage for a long-term advantage is not “logical”. There's nothing inherently illogical in accepting a short-term set-back if it makes the long-term success more likely.
  • The Straw Vulcan will be completely unable or unwilling to plan for unexpected and even illogical behavior from other parties.

More here.