The title of this paper sounds too promising, being too general and comprehensive. Its actual subject is more specific and restricted. The restrictions concern the scope of the analysis as well as its content. Restrictions of the scope are quite drastic. Due to them the account presented in the paper is illustrative rather than exhaustive. The approach to metaphysics characteristic of the Lvov-Warsaw School is exemplified by the doctrines of its three main representatives: Lukasiewicz, Kotarbinski and Ajdukiewicz. What is the reason for distinguishing those members of the School as the object of examination? It cannot be denied that they belong to the most eminent philosophers in the School — well-known and very influential. What is decisive, however, is the kind of their philosophical contribution: all of them are authors of highly original and ingenious philosophical doctrines. This cannot be said of other prominent members of the Lvov-Warsaw School: some of them were active as logicians, not philosophers (Lesniewski and Tarski may serve as outstanding examples), others contributed to the philosophical work done by the School in a way which did not involve the creation of new philosophical ideas.