When facing complex problems, most people habitually make small adjustments by referring to existing solutions. First principles offer another path: first break the problem down to its most basic level, then reason it back up from there. The difference between the two is that the former can only optimize within the existing framework, while the latter has the chance to change the framework itself.
Its core proposition
First principles emphasize starting from irreducible basic facts rather than from analogies or conventions. Analogies can help us make decisions quickly, but they also tend to inherit existing premises along with them. When external conditions have already changed, continuing to apply old premises naturally leads to skewed conclusions.
How to use it
Roughly three steps: first strip away the surface layers of the problem one by one and find its true underlying composition; then use objective laws to test which assumptions actually hold; finally recombine the verified elements. For example, to judge whether the cost of a service is reasonable, you can first break it down into the work steps that actually occur, rather than directly accepting the market price.
Boundaries of applicability
Not all problems are suitable for rebuilding from zero. When decomposition ignores the connections among elements and simplifies the system into isolated variables, conclusions become distorted; focusing only on underlying principles while ignoring real-world constraints also easily produces solutions that seem correct but cannot be implemented.
Difference from the analogical method
The analogical method has an advantage in efficiency: when encountering a similar problem, you directly refer to past practices, saving time and effort. Its risk lies in the fact that past practices were built on the premises of that time; when the premises change, the practices are often inherited unchanged. First principles require making these premises explicit and confirming one by one whether they still hold. The two methods are not mutually exclusive. Most everyday decisions can be handled quickly by analogy. Only when repeatedly hitting a wall by continuing old practices, or when the cost structure is clearly unreasonable, is it worth returning to first principles to reason through it again.
The value of first principles is to provide a clearer starting point for thinking, not a universal formula.