In consciousness studies there is a growing tendency to consider experience as (i) fundamentally affective and (ii) deeply interlinked with interoceptive and homeostatic bodily processes. However, this view still needs further development to be part of any rigorous theory of consciousness. To advance in this direction, we ask: (1) is there any affective type that is always present in consciousness?, (2) is it related to interoception and homeostasis?, and (3) what are its properties? Here we analyse and compare Jim Russell's (...) core affect and Thomas Fuchs' concept of vitality, and propose a more encompassing notion that subsumes both: continuous organismic sentience. It provides affirmative answers to questions 1 and 2, and, regarding question 3, a preliminary list of thirteen properties divided into ontological, phenomenological, and functional categories. This is the first of a series of studies that will systematically address different notions of a fundamental, homeostatically-rooted affective type, to achieve a rigorous, unified concept for consciousness science. (shrink)