Empiricism asserts that all knowledge is derived from sensory experience, emphasizing the role of observation and experimentation in understanding the world.

Plato's theory of Forms posits that the ultimate reality is the realm of eternal and unchanging ideas, which exist independently of the physical world.

René Descartes, a French philosopher, is known for his statement "Cogito ergo sum" (I think, therefore I am), which emphasizes the certainty of one's own existence as the foundation of knowledge.

Agnosticism is the belief that the existence or non-existence of ultimate reality or knowledge of it is unknown and perhaps unknowable.

Transcendental categories, according to Kant, are the fundamental concepts and principles that organize and structure human experience, such as time, space, and causality.

Existentialism is a philosophical movement that emphasizes the importance of individual existence, freedom, and choice, and the search for meaning in a seemingly meaningless universe.

Phenomenalism is the philosophical position that reality consists solely of phenomena, or appearances, and that we can only know our own subjective experiences, not the underlying reality.

The correspondence theory of truth asserts that a statement is true if and only if it corresponds to or accurately represents the actual state of affairs in reality.

Descartes, in his Meditations, argued that the only way to escape the skepticism of the senses is through the use of reason, which can provide certain and indubitable knowledge.

Solipsism is the philosophical position that the only thing that can be known for certain is the existence of one's own mind and that the external world is either a product of one's own consciousness or is unknowable.

Linguistic philosophy, also known as analytic philosophy, emphasizes the importance of language in shaping our understanding of reality and the limits of human knowledge.

Moral nihilism is the philosophical position that there are no objective moral values or that moral values are entirely subjective and relative to individuals or cultures.

Spinoza, in his Ethics, argued that the ultimate reality is a single, unified substance, which he called God or Nature, that manifests itself in diverse forms, including the physical world and human minds.

Pragmatism is a philosophical position that emphasizes the importance of practical consequences in evaluating the truth of a statement or the value of an action.

Heraclitus, a pre-Socratic philosopher, argued that the ultimate reality is a dynamic process of becoming, characterized by constant change and flux, rather than a static, unchanging entity.