I have noticed a common semantic stop-sign in physics: "But it doesn't predict anything."
This is often used whenever discussions of the foundations of a subject come up. I'm not saying that it's always bad to use this stop-sign; searching for predictive theories is definitely the most useful exercise in science.
But, thinking about the foundations of a subject can also be a very fruitful enterprise, even though you can't immediately see how it leads to predictive models. For example, Bell inequalities and quantum computing owe their origin, in part, to people debating the foundations of quantum mechanics. Also, the mathematical field of ergodic theory owes its origin to people thinking about the foundations of statistical mechanics.
Instead of saying "It doesn't predict anything" and then proceeding to ignore it, a more productive attitude would be to ask questions like: "So can we think of some kind of consequences that different foundational pictures point to?" or ask: "Can we build a nice mathematical framework in which we can talk about these questions?" or ask: "Do different pictures help me solve different kinds of problems?".
Instead of saying "It doesn't predict anything" and then proceeding to ignore it, a more productive attitude would be to ask questions like: "So can we think of some kind of consequences that different foundational pictures point to?"
Reworded: instead of saying "it doesn't predict anything", [we should] ask "does it predict anything?"
In other words: don't say a theory doesn't predict anything unless you have an actual argument that shows that it doesn't predict anything.
I think most of us are familiar with the common semantic stopsigns like "God", "just because", and "it's a tradition." However, I've recently been noticing more interesting ones that I haven't really seen discussed on LW. (Or it's also likely that I missed those discussion.)
The first one is "humans are stupid." I notice this one very often, in particular in LW and other rationalist communities. The obvious problem here is that humans are not that stupid. Often what might seem like sheer stupidity was caused by a rather reasonable chain of actions and events. And even if a person or a group of people is being stupid, it's very interesting to chase down the cause. That's how you end up discovering biases from scratch or finding a great opportunity.
The second semantic stopsign is "should." Hat tip to Michael Vassar for bringing this one up. If you and I have a discussing about how I eat too much chocolate, and I say, "You are right, I should eat less chocolate," the conversation will basically end there. But 99 times out of a 100 nothing will actually come out of it. I try to taboo the word "should" from my vocabulary, so instead I will say something like, "You are right, I will not purchase any chocolate this month." This is a concrete actionable statement.
What other semantic stopsigns have you noticed in yourself and others?