A mind all logic is like a knife all blade: it makes the hand bleed that wields it.
— Rabindranath Tagore
A 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 writers are more concerned with setting up their straw man 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 is Literal-Minded. Note that the idea that an "intelligent" character wouldn't "get" the concept of metaphors, idioms or sarcasm isn't very logical.
- The Straw Vulcan cannot believe in the paranormal. Logical enough in Real Life, where the existence of such forces are debated, but this can lead to such characters coming off as being blind or in denial if they live in a universe where such things are shown to be real.
- The Straw Vulcan will often commit the Fallacy Fallacy, dismissing a conclusion simply because it was based on invalid logic or on emotion. While the fact that an argument contains a fallacy is grounds for dismissing an argument, it does not prove that the conclusion is wrong.
- 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. Spock and Tuvok both did this regularly in the various Star Trek works. Although they didn't say it outright, whenever they mentioned having calculated low odds for the success of a given plan, it was obvious that they did not believe said plan should be attempted. This was typically responded to by one of the humans saying the equivalent of, "damn the torpedoes!" which was intended to prove that said human characters were inherently irrational.
- The story assumes that anything which doesn't fit a particular mathematical model of logic isn't "logical". Related to the Perfect Solution Fallacy, again, because you can only find truly perfect 1=1 solutions and conceive of perfect circles in abstract mathematics.
- Related to the Perfect Solution Fallacy: The Straw Vulcan will proceed to disturb everyone with doomsaying that their current plan "only has a 10% chance for us to succeed", and then the emotional protagonist proceeds to disprove him by saying "Never Tell Me the Odds" and succeeding. Actually, when all other options are depleted, the plan that has a 10% chance of success is logically superior to other courses of action that have less chance of success. (And presumably doing nothing means a 0% chance) Bothering people with remarks about low chances of success in critical situations may degrade their morale and thus further diminish said chances, so it doesn't make logical sense to quote poor odds unless there's a better option that can be taken. Pessimism for pessimism's sake in a time of need simply isn't logical, no need to be the sensitive guy of the cast to figure that out.
- In general, Straw Vulcans will often act as The Cynic and consider the more idealistic choice as illogical and improbable, even though there's no direct logical connection between logic and pessimism. While many logicians are human and can be driven cynical (especially when they're the Only Sane Man or are logically justified by a painful life), logic itself does not lean on either side of the Sliding Scale of Idealism Versus Cynicism.
- There's also the case where the emotional person suggests a course that shouldn't work, period, but the Straw Vulcan's ideas all involve some aspect that the "non-logical" character find cynical or objectionable. So Straw Vulcan is outvoted, they go with the dumb emotional plan, and lo, it works... due to sheer dumb luck. This is then lauded as a victory for emotion, when in fact it's a victory for the Million to One Chance principle.
- The Straw Vulcan will be completely unable or unwilling to plan for unexpected and even illogical behavior from other parties. Perhaps the most common flaw of the Straw Vulcan is their inability to draw upon any knowledge which comes from being an emotional being. They seem unable to factor emotions, or any associated information, into their analysis; they are not so much "logical" beings as beings without a functional understanding of the nature of emotional processes.
- The Straw Vulcan, and by extension all logical thinkers, will be uncreative, or at least less so than emotional people. He will be unable to come up with an imaginative answer to an unusual problem, while the emotional protagonist, often despite having no real experience with this kind of situation, will be able to save the day. This is supposed to show that "logic" is inferior to "emotion" in that emotion can provide a third and more favorable option to the logician's bad and worse options.
- The Straw Vulcan assumes that self-sacrifice isn't "logical", even though there can easily be situations where self-sacrifice is "logical".
- A Straw Vulcan will have to consider everything about the problem in full detail even in time-critical situations, while the emotional person will make the snap decisions necessary in this sort of situation. This will demonstrate how the "logical" Straw Vulcan is useless under pressure and therefore inferior to the emotional protagonist. The obvious flaw is that it's patently illogical to ignore time constraints in this manner. The technical term for this is "bounded rationality", as opposed to "classic rationality" which does assume that you have infinite time to gather information and consider.
- 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. (This is in fact studied in algorithmics: a step that visibly takes you closer to the goal may eventually run you into a dead end if you don't consider alternatives.).