I think of it a little differently. Human or animal intelligence here is a somewhat useful reference point. As an analogy, think of the first steam engines. Th

I think of it a little differently. Human or animal intelligence here is a somewhat useful reference point. As an analogy, think of the first steam engines. They were replacing horses so why not measure their primary function in units of horse power? We had a somewhat rigorous physical framework for work and power but it probably wasn't well understood by the target audience to be useful. While we don't seem to have a scientifically rigorous definition of intelligence we still can have a somewhat useful discussions about utility in reference to another familiar instance of intelligence.