A hypothesis is presented according to which structure of consciousness is quadri-dimensional. The four dimensions are duration, quality, intensity, and affectivity. One may reach this conclusion by introspection alone, or by deduction along the following steps: (1) consciousness should be examined from the point of view of evolutionary psychology; (2) this leads to the following postulate--consciousness evolved from sensation; (3) the postulate entails a corollary-- consciousness has kept the quadri-dimensional structure of sensation. The above postulate could explain the phylogenetic origin of pleasure as the common currency, and in turn the tradeoffs for access to the behavioral final common path. It would also entail that joy is the transient sign of a useful conscious event, whereas happiness is the indifferent experience of a satisfied mind.