  Intelligence is a difficult concept to define, despite many attempts at doing
so. Rather than trying to settle on a single definition, this article
introduces a broad perspective on what intelligence is, by laying out a cascade
of definitions that induces both a nested hierarchy of three levels of
intelligence and a wider-ranging space that is built around them and
approximations to them. Within this intelligence space, regions are identified
that correspond to both natural -- most particularly, human -- intelligence and
artificial intelligence (AI), along with the crossover notion of humanlike
intelligence. These definitions are then exploited in early explorations of
four more advanced, and likely more controversial, topics: the singularity,
generative AI, ethics, and intellectual property.
