In theory there is no difference between theory and practice; in practice there is.
The self-swallowing structure is the point: the claim that theory and practice agree is itself a piece of theory, and the exception it admits is the whole of the difficulty. What it names is the gap between a model's stated assumptions and the conditions under which it is actually applied, which is where most failures of applied knowledge occur.
In practice
- A process that works on the whiteboard meets the one supplier who will not use the format.
- A model validated on clean data meets the data the organisation actually keeps.
- Possible explanations
- The explanation is that theory omits what it takes to be irrelevant, and practice is where the omitted details turn out to matter, so the gap is built into the act of modelling.
- In its favour
- The self-swallowing structure makes the point efficiently, and the observation is confirmed daily in engineering, medicine and software.
- Against it
- It is a joke rather than a claim, offers no account of which omissions will matter, and its attribution is disputed between several sources and established for none.
- Standing
- Attribution is disputed between several sources and is not established for any of them.
- Subject
- Science & Epistemology
- Essay
- Paradoxes in the data, and sayings about knowing