A case is made that measures used in quality of life and happiness research will be essentially unidimensional: inherently tapping minor dimensions. This is illustrated using Diener's Satisfaction with Life Scale (SWLS). It is shown that the SWLS does not meet the standard of strict unidimensionality, but that the interpretation of the total scale score is not compromised because the additional dimensions are relatively minor. In the context of the example, a multi-step strategy is described that allows researchers to test for essential unidimensionality. Throughout the article, essential unidimensionality is contrasted with the received view of strict unidimensionality and confirmatory factor analysis methods.