Final answer:
The branch of metaphysics focused on the nature of being and existence, both material and spiritual, is known as ontology. It addresses fundamental questions of reality, being, and the origins of things, allowing for an exploration of existence beyond the physical world.
Step-by-step explanation:
Branch of Metaphysics Studying the Nature of Being
The branch of metaphysics that studies the nature of being, or anything that exists materially or spiritually, is known as ontology. Ontology interrogates fundamental questions such as 'What exists?', 'What is real?', and 'What does it mean to be?'. It encompasses concepts that include physicalism and naturalism - ideas which assert that reality is, respectively, either strictly material or composed of lifeless, non-experiencing energy. Metaphysics itself seeks to provide a comprehensive description so simple and all-inclusive that it applies to everything, whether it's considered divine, human, or any other entity.
Ontology, as a subdivision of metaphysics, entertains various metaphysical questions about the existence of god, soul, mind, and time, among others. It also probes into the origins of reality, including the emergence of matter, space, and time as part of cosmology, and delves into values via axiology. Notably, the study of ontology and metaphysics as a whole allows individuals to explore the nature of existence beyond just the physical world, addressing concepts that are deeply philosophical and abstract.