One of the known issues in the field of Artificial Intelligence is that there is no generally accepted formal or informal definition of intelligence.

I have learned about this problem from Legg & Hutter and Chollet.

Each of these two papers proposes a definition for machine intelligence:

Def. 1 [Legg & Hutter]: The ability to achieve goals in a wide range of environments.

Def. 2 [Chollet]: The intelligence of a system is a measure of its skill-acquisition efficiency over a scope of tasks, with respect to priors, experience, and generalization difficulty.

Both papers start with a review of previous attempts at defining intelligence, and then proceed to present a proposal for a formal definition.

One point of disagreement is whether the definition for machine intelligence should capture only human-like intelligence [Chollet] or more general, non-human types of intelligence, Legg & Hutter call this Universal Intelligence [Legg & Hutter].

Differences between definitions

The agent under Def 1.

  • it does not need know the initial prior
  • it aims to be maximally intelligent for any given environment, in other words, Universal

The agents under Def 2.

  • it aims at emulating human-like intelligence
  • relies on its builder to provide and control priors
  • the provided priors are human priors


  • arXiv:0712.3329v1 - Shane Legg, Marcus Hutter, Universal Intelligence: A Definition of Machine Intelligence
  • arXiv:1911.01547v2 - François Chollet, On the Measure of Intelligence