An Introduction gives the approach to the subject by posing the following questions: what is the psychological process at the basis of the experience of beauty; from what particular psychic situation does it originate; what specific emotional reaction leads to the experience of beauty? It is then not so much beauty itself as the psychological experience connected with all phenomena to which we attribute beauty—such as rhythm, symmetry, repetition—which Sachs is investigating. He says: 'We can divide [the] beauties of nature into two classes. The first one where beauty appears to be within the scheme and purpose of nature… The second class emerges out of a combination of circumstances which we cannot conceive as the consequence of a development or of a "plan", but which appear at random, "purely accidentally".' To