Although a large part of happiness is looking forward to something, this aspect of happiness has remained largely unexplored and unexplained. The bulk of the attempts to explain it so far have come from fields such as neuroscience, music and psychology. Furthermore, as a phenomenon anticipation has been variously conceived and studied under different names, such as hope, expectation, prospection, and similar. This current work attempts to fill the knowledge gaps and to provide a deepened understanding of the phenomenon of anticipation from the philosophical perspective. The effort has been able to formulate a single theory that integrates the different conceptions into a unified theory of expectation. This integration has itself gone on to support a unified understanding of the phenomena of boredom, anxiety, peace, habituation/adaptation, and set-point. It arises from logical analysis, and hence, being based on simple and flawless logical foundations, is able to provide a philosophical and scientific basis for understanding these phenomena which core themes in positive psychology are. But the work‘s ultimate achievement is that it has been able to establish an articulate definition of happiness and suffering. By logical analysis of the phenomenon of anticipation, The Science of Expectation grounds the meaning of happiness – and naturally also explains the way to it! In the final analysis it identifies happiness as peace and suffering as worry or anxiety. And it posits that the way to peace is to lower expectation, or in practical terms, to live lowly.