Continuum theories or models explain variation as involving a gradual quantitative transition without abrupt changes or discontinuities. It can be contrasted with 'categorical' models which propose qualitatively different states.
In physics, for example, the space-time continuum model explains space and time as part of the same continuum rather than as separate entities. A spectrum in physics (e.g. of light) is often termed either a 'continuous spectrum' (energy at all wavelengths) or 'discrete spectrum' (energy at only certain wavelengths).
In psychology, theories of mental phenomena can propose discrete differences between individuals (e.g. everyone has certain personality traits and not others) or a continuum (e.g. everyone lies somewhere on a particular personality dimension). This can also apply to fields such as law or sociology or ethics in explaining or judging variation in human behavior.
In psychiatry, categorical models seek to distinguish and define particular mental disorders or illnesses, whilst continuum or dimensional models propose that some people are more extreme than others on particular dimensions.
Mindstream is a continuum theory in Buddhist philosophy. In Vajrayana (Tantric Buddhism) it may be understood as an upāya (Sanskrit) doctrine of the nonlocal and atemporal as resolved into a qualification of omnipresent. The lexical item 'Moment', has been employed in the sense of its etymon "momentum" though the 'stream', 'array' or 'procession' is atemporal and nonlocal or 'quanta of consciousness' (Tibetan: thig le; Sanskrit: Bindu) proceeding endlessly in a lifetime, between lifetimes (Tibetan: Bardo), from lifetime to lifetime, prior to engagement in the Bhavacakra of Samsara and beyond as an inclusive continuum (Tibetan: rgyud) rather than an individuated, separate, or discrete perceptual, cognitive, or experiential entity, as in the conception of the Ātman. Waldron (undated) states:
Indian Buddhists see the 'evolution' of mind i[n] terms of the continuity of individual mind-streams from one lifetime to the next, with karma as the basic causal mechanism whereby transformations are transmitted from one life to the next.
Dzogchen Rinpoche establishing the processive reciprocality of the training of the mindstream and the Buddhadharma, holds that:
The Buddhadharma is a process, one through which we train and tame our own mindstreams. One approach is to go to the root of what we mean by "I", our sense of self or individual self-identity.<ref>Rinpoche, Dzogchen (2007). Taming the Mindstream in Wolter, Doris (ed.) "Losing the Clouds, Gaining the Sky: Buddhism and the Natural Mind." Wisdom Publications. ISBN 0861713591 p.82-83 Source:  (accessed: July 29, 2008)</ref>
Thanissaro Bhikkhu in contextualizing and redressing what he believes to be the general misconception of anātman (rendered as "no self") and ātman (rendered as "self"), in relation to the view he holds of the intention of Shakyamuni Buddha, states:
This clear evocation of what later became canonized in Buddhist discourse as Madhyamika or "middle way", is key to tender a description of the ineffable Mysterium Magnum of the "Great Continuum" that is rendered in English as "Mindstream": the nondual resolution of ātman and anātman.
...the Buddha was asked point-blank whether or not there was a self, he refused to answer. When later asked why, he said that to hold either that there is a self or that there is no self is to fall into extreme forms of wrong view that make the path of Buddhist practice impossible.<ref>Bhikkhu, Thanissaro (1996). No-self or Not-self?. 
In the entwined Dzogchen traditions of Bönpo and Nyingmapa, the Mindstream is constituted by a continuum of gankyil comprised of the Five Pure Lights of the Five Wisdoms which unite the trikaya. These 'tantric correlations' (or Twilight Language) are evident in the iconographic representation of the Five Jinas(The Twilight Language: Explorations in Buddhist Meditation and Symbolism. Curzon Press: London. ISBN 0-312-82540-4) and the saṃpanna-krama of the gankyil and mandala in Dzogchen sādhana. The 'supreme siddhi' or 'absolute bodhicitta' of the Dzogchenpa is when the Mindstream of their 'bodymind' (a rendering of namarupa) is 'released' (a rendering of Nirvana) as the Rainbow Body.