Intelligence is not only the ability to reason; it is also the ability to find relevant material in memory and to deploy attention when needed.

Intuition does not denote something contrary to reason, but something outside of the province of reason.

Intelligence consists in ignoring things that are irrelevant.

Intelligence, then, is the ability to attain goals in the face of obstacles by means of decisions based on rational (truth-obeying) rules. The computer scientists Allen Newell and Herbert Simon fleshed this idea out further by noting that intelligence consists of specifying a goal, assessing the current situation to see how it differs from the goal, and applying a set of operations that reduce the difference. Perhaps reassuringly, by this definition human beings, not just aliens, are intelligent. We have desires, and we pursue them using beliefs, which, when all goes well, are at least approximately or probabilistically true.

Intelligence is not the ability to store information, but to know where to find it.

The true sign of intelligence is not knowledge but imagination.

Historically, people have been naive about what qualities, if mechanized, would undeniably constitute intelligence. Is intelligence an ability to integrate functions symbolically? If so, then AI already exists, since symbolic integration routines outdo the best people in most cases.
If intelligence involves learning, creativity, emotional responses, a sense of beauty, a sense of self, then there is a long road ahead, and it may be that these will only be realized when we have totally duplicated a living brain.

Intelligence is what you use when you don't know what to do.

The actual operation of intelligence is thus beyond the possibility of being determined or conditioned by factors that can be included in any knowable law. So, we see that the ground of intelligence must be in the undetermined and unknown flux, that is also the ground of all definable forms of matter. Intelligence is thus not deducible or explainable on the basis of any branch of knowledge (e.g., physics or biology). Its origin is deeper and more inward than any knowable order that could describe it. (Indeed, it has to comprehend the very order of definable forms of matter through which we would hope to comprehend intelligence.)

Intellect is not going to be your home. It is a small instrument, to be used only for passing from instinct to intuition. So only the person who uses his intellect to go beyond it can be called intelligent. Intuition is existential. Instinct is natural. Intellect is just groping in the dark. The faster you move beyond intellect, the better; intellect can be a barrier to those who think nothing is beyond it. Intellect can be a beautiful passage for those who understand that there is certainly something beyond it.

Intelligence is the capacity to perceive the essential, the what is; and to awaken this capacity, in oneself and in others, is education.

Intelligence is quickness to apprehend as distinct from ability, which is capacity to act wisely on the thing apprehended.

Imagination is but another name for super intelligence.

“Intelligence” demands the most strict of definitions, since the word is easily and often abused. Intelligence rates the quality of Gaean man’s competence at altering environment to suit his convenience, or, more generally, the solution of problems. The corollaries to the idea are several. Among them: In the absence of problems, intelligence cannot be measured. A creature with a large, complicated brain is not necessarily intelligent. Raw abstract intelligence is a meaningless concept.