It is shown through examples ranging from Parmenides and Plato to Whitehead and Wittgenstein that beauty is central among the values that have made metaphysical theories appealing and credible. A common attitude would be that the aesthetic properties of metaphysical theories may be important for effective presentation but are irrelevant to the cognitive value of the theories. This however is question-begging, since it assumes without argument that ultimate reality is indifferent to value-considerations such as beauty. If on the contrary we allow that the aesthetic properties of theories may be cognitively relevant, which such properties should be considered? This question is explored in the final section of the paper.