Any explanation of an observed phenomenon which, while not 100% scientifically accurate, is simple enough, and just accurate enough, to convey the beginnings of understanding to anyone who is new to the subject. There is always time to fill them in on the fine detail further down the road. This describes the sort of axioms we tell young children when they are beginning to get to grips with science.
"A “lie-to-children” is a statement which is false, but which nevertheless leads the child’s mind towards a more accurate explanation, one that the child will only be able to appreciate if it has been primed with the lie."
"Yes, you needed to understand that” they are told, “so that now we can tell you why it isn’t exactly true”(The Science of Discworld, Ebury Press edition, quotes from pp 41-42)
There are many well known lies-to-children including that electrons orbit the nucleus like a little solar system, DNA looks like a spiral ladder and Albert Einstein's hair having something to do with his discovering the theory of relativity.
There are several sub-sets of “lies to children”.
If a “lie-to-children” can be summed up in terms of “as much as they can understand” then there are also
- Lies-to-bosses (“as much as they need to know” or, “we operate on a “need to know” basis, and the boss doesn’t need to know”)
- Lies-to-patients (“they won’t worry about what they don’t know”)
- Lies-to-ourselves (we all do it: every time we think in terms of “A chocolate you don’t like the flavour of doesn’t count as chocolate” or “food consumed while walking contains no calories”)
Hex, the Unseen University's equivalent of a supercomputer, has expanded the concept to include Lies-To-Wizards. This makes Hex more able to get a tricky theoretical concept across to the Wizards than Ponder Stibbons, who conscientiously tries to tell them the whole truth.