General terms:
* Metaphysics: This is the branch of philosophy that explores fundamental questions about reality, existence, and knowledge. It often delves into the nature of being, time, space, and causality, which are related to ultimate nature.
* Axiology: This is the branch of philosophy that studies values, including moral, aesthetic, and religious values. It explores the nature, foundation, and justification of values, which relate to significance.
More specific terms:
* Philosophical anthropology: This field explores the nature of human beings, their place in the universe, and their ultimate purpose.
* Cosmology: This field investigates the origin, evolution, and structure of the universe. While focusing on the physical universe, it can also touch upon questions about its ultimate nature and meaning.
* Theology: This field deals with the study of God, religion, and the divine, often exploring the ultimate significance of existence and human life.
* Existentialism: This philosophical movement emphasizes individual freedom, responsibility, and the search for meaning in a seemingly absurd world.
Ultimately, the best term depends on the specific questions you are trying to answer and the perspective you are taking.
