 The three authors described just above deny that consciousness is binary for very different reasons, and each of their views is controversial. Further, none of them offers much in the way of tools or concepts for thinking about the putatively nonbinary nature of consciousness. Following up on Lycan's suggestion of degrees of richness or fullness, one might ask what graded dimensions or qualitative thresholds might be available to distinguish different kinds of minds? Various authors have distinguished between ‘primary’ and ‘higher order’ consciousness (Seth et al. 2005); ‘primary’, ‘secondary’, and ‘tertiary’ consciousness (Panksepp 2005); and ‘core’ and ‘extended’ consciousness (Damasio 1999). However, most of these authors seem to correlate phenomenal consciousness, i.e. having any subjective experience at all, with primary or core consciousness. The terms “secondary” and “tertiary” are supposed to pick out elaborated forms of consciousness. Hence it is not clear that any of these taxonomies are at odds with the idea that phenomenal consciousness itself is binary — either wholly present or wholly absent for a given system. However, the issue deserves more scrutiny, as it bears on the problems of the distribution and evolutionary origins of consciousness. If consciousness is non-binary, then the distribution of consciousness will not be sharply bounded, but will include gradations — some animals may be partially or incompletely conscious. 