One of my favorite quotes of all time comes from Mary Catherine Bateson:
"Few things are more debilitating than a toxic metaphor."
The reason for this is that humans think mostly through metaphor. In fact, as you are reading this sentence, you are thinking in metaphor - the language in the sentence isn't the thing itself, but only a metaphorical representation of the thing. (For a better example, think of the word "apple" - the word is a symbol that represents a pattern of existence but not the pattern itself)
I was reminded of this when reading a paper on Jeffrey Rosenthal's website. The paper was titled: How Probability Theory Nearly Destroyed Canada. Unfortunately, if you read the article (which is worth a read), you'll realize that it's not probablility theory that's at fault here, but the choice of a toxic metaphor by the Canadian Prime Minister.
The choice of metaphors is one that is often taken lightly - we make metaphorical comparisons all the time. And, often, the metaphors we choose bring unintended consequences.
As a (really banal and mundane) example, I recently was talking with my wife about how easy it seems for the cats to eat soft cat food. I said: "it must be like McDonald's food for cats - it's designed to be easy to eat quickly and in large portions". And Melina, hearing only my metaphor, immediately started to explain the health benefits of the food - how it was far healthier than a Quarter Pounder with Cheese, and she wouldn't buy that kind of food for our cats.
This is a great example of a time when I had chosen the metaphor without much thought, and it brought with it unintended consequences - I was speaking only about the emptiness of the food (in terms of density), rather than nutritional content - but the metaphor I chose brought forth a whole other set of connotations.
I'll leave it as an exercise to the reader to discover where your metaphors have brought similarly unintended consequences in some conversation or project in your life.