The book "Is Intelligence an Algorithm?" shows that in attaining complexity, nature, humans and machines follow a series of predictable steps. In this book I boldly named this the "Intelligence Algorithm", but I also showed that the creative aspects thereof can't really be captured in terms of algorithms.
The definition I used for Intelligence, the ability to achieve complex goals, is also a definition which made the framework for arguing my point very broad and allowed to come to the conclusions presented. But this "intelligence" is not what the average person would understand to be intelligence. When Nature evolves or when machines solve complex problems, there is no understanding or awareness involved of what is being done, how it is done and why it is done. Wikipedia describes Intelligence among others as "the capacity for logic, understanding, self-awareness, learning, emotional knowledge, planning, creativity, and problem solving". This definition mostly requires a conscious agent, who knows what is going on.
Wikipedia also gives a more generalised definition of Intelligence as follows: "the ability or inclination to perceive or deduce information, and to retain it as knowledge to be applied towards adaptive behaviours within an environment or context."
Although the definition of information has also been expanded for computer science to merely relate to the answer of some question, if we ignore that definition for the moment, we can perhaps state that originally the terminology implied that there was a conscious receiver who was able to decode the information, so that it made sense to him/her. Knowledge also implies that there is a conscious knower, who can make sense of the knowledge. Behaviour certainly is a trait of conscious agents. Therefore also this more generalised definition would have been interpreted as an ability of a conscious agent before the advent of AI. It is because of the developments in computer science that we have started the semantic drift leading to broader definitions of terminologies such as information, knowledge, learning and intelligence. But at the beginning of the 20th century intelligence would have been understood as an ability of a conscious agent.
This long introduction is necessary to prepare you for one of the points I wish to make in this essay: If we were to restrict intelligence to the narrower definition being "the conscious ability or inclination to perceive or deduce information, and to retain it as knowledge to be applied towards adaptive behaviours within an environment or context", would we still be able to speak of an "intelligence algorithm"? Or in other words, are intelligence and algorithms not two irreconcilable and opposed aspects of the ability to achieve complex goals? The algorithm merely requiring a dumb mindless execution of a set of fixed instructions and intelligence a conscious investment that can adapt to unknown situations for which there are no fixed rules?
Read more of this in "Is Intelligence an Algorithm? 2"