After over twenty years of waiting, the great work of Mario Bunge reaches Spanish-speaking readers. The Treaty of philosophy? In 8 volumes (1974-1989)? It is certainly one of the most ambitious projects of modern philosophy. Your goal is to build a philosophical system which the author considers the core of contemporary philosophy (semantics, ontology, epistemology and ethics), with special attention to the problems posed by scientific and technical knowledge. Their tools are mathematical and scientific knowledge itself. The result is a Herculean work is distinguished by its originality, systematic, thematic breadth and formal rigor, attributes that make it a must for the student of philosophy. This volume is the third philosophical brick building built by Mario Bunge. Here ontology (or metaphysics) is not "a speech (in ancient Greek or modern German) about Being, Nothingness and Dasein 'or a collection of instinctive or impossible to test beliefs; much less the study of spiritual beings. For Bunge, ontology is a science, more precisely the general science of being and becoming. This approach dissolves at a stroke one of the highest logical empiricism and falsifiability problems: finding a clear boundary between science and metaphysics. And since partially shared objectives metaphysics and science have to use a common method: the general method of science. Here are a handful of questions that explores the bungeana ontology: What is one thing ?; What are the universal ?; Is there natural kinds ?; Is there a chance or the odds are simply the measure of our ignorance ?; Can there be space without things? And what is the mind? Although for the answer to this last question, the reader should expect to Volume 4 of this treaty: Ontology II: A world of systems