Seventeen original essays are grouped under five headings. Three introductory chapters present higher-order languages and motivate their use in metaphysics. Three chapters on pure higher-order metaphysics discuss different options of higher-order languages and logics which may be used in metaphysics. Three chapters on applied higher-order metaphysics consider the application of higher-order logic to various central topics of metaphysics. Three historical chapters trace the development of higher-order logic as it relates to metaphysics over the last 150 years. The volume concludes with a discussion, containing two chapters criticizing the use of higher-order logic in metaphysics, as well as responses to these criticisms by two authors.