"Is this a science problem, or an engineering problem?"
Reading the lengthy discussion of this distinction in Eric Drexler's Radical Abundance made problems in several projects I've worked on recently seem much more solvable.
Science and engineering are inseparable domains of thought and action, linked by a shared language of mass and energy, molecules and thermodynamics, physical systems and physical law. This shared language makes communication deceptively easy — easy, because scientists and engineers can see every detail in the same way; deceptive, because they see these details in different contexts, forming different patterns and presenting different problems. In a fundamental sense, science and engineering are antiparallel, facing in opposite directions. The resulting gaps in understanding can open a chasm wide enough to trip a manager, or to swallow a project. [Emphasis added]
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While science aims (ideally) to produce exact descriptions of all parameters of all members of a general class of physical systems, engineering aims to manufacture instances of a single kind of system, making choices to ensure that its functional parameters will equal or exceed those specified by a design description.
Likewise, while science aims to formulate a single theory that exactly fits all parameters of every description, engineering aims to design at least one description of a system having functional parameters that equal or exceed those required by one of a potential multiplicity of system concepts.
In this connection, is a proliferation of possible ways of satisfying a constraint good, or bad? In science, finding more possibilities creates greater uncertainty; in engineering, finding more possibilities provides greater freedom of design. This is a basic question with opposite answers — and there are many more.
Science and engineering share a language of physical systems and physical law, but they ask different questions, seek different knowledge, and serve different ends. The ramifications range from different views of the non-linear system dynamics to differences in working relationships and institutions. The consequences are pervasive and deep, familiar and surprising, and extend far beyond what I have sketched here.
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See also: Boring Advice Repository, Solved Problems Repository, Grad Student Advice Repository, Useful Concepts Repository, Bad Concepts Repository
I just got back from the July CFAR workshop, where I was a guest instructor. One useful piece of rationality I started paying more attention to as a result of the workshop is the idea of useful questions to ask in various situations, particularly because I had been introduced to a new one:
"What skill am I actually training?"
This is a question that can be asked whenever you're practicing something, but more generally it can also be asked whenever you're doing something you do frequently, and it can help you notice when you're practicing a skill you weren't intending to train. Some examples of when to use this question:
Many of the lessons of the sequences can also be packaged as useful questions, like "what do I believe and why do I believe it?" and "what would I expect to see if this were true?"
I'd like to invite people to post other examples of useful questions in the comments, hopefully together with an explanation of why they're useful and some examples of when to use them. As usual, one useful question per comment for voting purposes.