My sense is that everyone is pretending Intelligence doesn't have a grounded definition, from which all other definitions arise:
- Intelligence is a measure of utility in an action space μ(υ)
It can be a relative measure, in relation to other rational agents, or absolute in relation to solved games (problems). An action space is any context, and formalized as problems or sets of problems, typically grouped by complexity class.
Hutter and Legg is an explication of this grounded definition which accounts for unlimited contexts (complexity classes/environments) and for increasing utility of a given agent over time (learning/optimization.) Intelligence itself does not require learning or general applicability, but Hutter & Legg does not refute this, merely grades static intelligence and narrow intelligence as more limited.
Even this is subject to context, as more limited rationality can be more optimal.
- The definition of intelligence is grounded because, while the term "intelligence" is a symbol, intelligence itself is function, the strength of which evaluated by a measurement of some result (utility)
It doesn't require defining the function to understand it as a function: measurement of a result requires mechanism and decision/action.
You will find this natural language definition applies to even emotional intelligence, which relates to the observational capability of the rational agent in context, and allow that rational agent to make more optimal decisions in context.
This is similar in spirit to truth, only grounded in a formal logic context, where it is a condition and result, not an assertion. By contrast, the the conditionality of truth is often obscured in a natural language context, where is is routinely applied to unvalidatable informal statements, and can even be conflated with the statement itself à la: "this is the truth!"