What makes a specific principle useful?
When I began to think about principles, I developed a quick way to identify if a principle was useful to me in my everyday life. It's what I have called the Principles Feedback Loop. This feedback loop has been useful for revisiting and evaluating principles over time.
The feedback loop works as follows:
1) Identify a principle that comes from my own ideas or the ideas of others.
2) Define how the principle can be put into action
3) Take those series of actions and organize them into a series of practices or habits
4) Determine the outcome of the practices over time
These four Steps have been helpful in evaluating the validity of any principle that I come across.
There are multiple break points within the feedback loop. For example, you can identify a very helpful principle that isn't put into immediate action, or if you do put the principle into action you may not develop the practices necessary to achieve the outcome you expect. In many cases, the principle is helpful at face value but the actions and practices built around it fall short of expectation. The idea of garbage-in, garbage-out applies here where fundamentally, if we have a severely flawed principle, no amount of action or practice will achieve a positive outcome.
General vs Specific Principles
The idea of evaluating usefulness of different principles brought me to the idea that there is a spectrum that most principles fall in between. A principle can be considered more general or more specific, depending on its' application.
General principles are those that generally work for everyone or generally work in most situations. Examples of general principles would be sayings such as "You reap what you sow", "Design things with the user in mind", or "Reward good behavior and discourage bad behavior". General principles are usually the kinds of principles taught in early education and are more widely available. Benjamin Franklyn's Poor Richard's Almanac was popular because it promoted general principles that anyone could adopt. Many popular figures today promote general principles in order to relate to a large audience.
Specific principles are those that apply to a particular concept or context. These specific principles are usually packaged in a school of thought that surround it. In the world of finance and economics you have the Keynesian economists who are in contrast to the Austrian school of thought. Yes, these are two larger schools of thought, but then they filter down into specific sub groups that promote different practices. The Keynesian's could promote government infrastructure projects, economic stimulus and buying government debt while the Austrian's would promote buying precious metals, small business growth and local economies. Both may not be mutually exclusive, but the principles that each school promotes are fundamentally different. You will see specific principles promoted in any area where a skill or craft is involved.
Just as you can take a general principle and make it more specific to your application, you can take a specific principle and generalize it in order to apply it into a different context. In other words, general principles have a "High Transferability" where you can transfer the principle to many different contexts or applications, and specific principles have a "Low Transferability" where it is very applicable for a particular situation but difficult to apply more broadly.