 Plato built on the ancient common sense that connected pleasure with the satisfaction of felt longing, or appetitive desire (epithumia), and also on early scientific speculation equating pleasure with the fulfillment of bodily needs. He observed that simple personal-report level motivational accounts fail because we may experience pleasure without any previously felt distress, desire, or noticed need, as sometimes when looking, listening, smelling, or learning, and also that one may fulfill physiological needs without experiencing pleasure in the process of so doing (Philebus 51A–52C). He therefore refined and generalized the current physiologically-influenced account of pleasure as restoration of bodily imbalance or deficiency, on the model of hunger and thirst, to make it instead the sensation, perception, or consciousness (all aisthēsis in Greek) of return from a (possibly unnoticed) state of deficiency to a naturally healthy  state.[13]  The ‘pure’ (‘unmixed with pain’) pleasures of knowing and perceiving were apparently construed as signaling the satisfaction of needs we are unaware of, and so not pained by, acquiring or having. A unified account of all pleasure was thus achieved, as awareness of processes of fulfilling very diverse needs, systematically accounting for both pleasure’s unity and diversity. Pleasure could be accorded a place in the best life attainable for beings like ourselves, imperfect enough to have recurrent needs but sometimes aware of their however partial and temporary satisfaction. But the absolutely best life would be a divine one of permanent perfect knowing without the possibility of further learning or any other improvement, and in which there would therefore be no pleasure at all – and presumably we would do well, insofar as we are able, to approximate to this (Philebus 33B). Descartes’ views of the function or content of pleasure and Spinoza’s official definitions of pleasure as an affect of transition to greater perfection are close to Plato’s, as also are one of Kant’s  characterizations,[14]  one of Elijah Millgram’s (2000, pp. 122–26), and Timothy Schroeder’s (2001, 2004, discussed in §3.1). Such Improvement Indicator Views may account for diversity within pleasure by the different species of improvements indicated. But they need not attribute explicit awareness of needs or of their fulfillments as such to the experiencing subject. A modern version might attribute only biological functions, without requiring any explicit representation of departures from or restorations to one’s natural state at either personal or subpersonal levels.