David Hume is credited with formulating the Problem of Induction, which challenges the reliability of inductive reasoning and the assumption that the future will resemble the past.

Solipsism is the philosophical view 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 the mind or unknowable.

Empiricism is the epistemological theory that emphasizes the role of sense experience and observation in acquiring knowledge, rather than relying solely on reason or innate ideas.

Relativism is the philosophical position that claims that knowledge is subjective and relative to the individual, group, or culture, rather than being objective and universally true.

René Descartes is known for his rationalist approach to epistemology, arguing that true knowledge can only be obtained through rational thought and deduction from self-evident principles, such as the existence of the self ('I think, therefore I am').

Skepticism is the philosophical position that claims that knowledge is impossible, either because of the inherent limitations of human perception and understanding or because of the lack of objective criteria for truth.

Immanuel Kant argued that the only way to overcome skepticism is through the transcendental unity of apperception, which is the unity of consciousness that synthesizes the manifold of experience into a coherent world.

Positivism is the philosophical position that claims that knowledge is limited to what can be verified through sense experience and observation, rejecting metaphysical and theological claims that cannot be empirically verified.

Plotinus, a Neoplatonic philosopher, argued that the only way to achieve true knowledge is through mystical experience and intuition, which allow one to transcend the limitations of sense experience and reason.

Constructivism is the philosophical position that claims that knowledge is socially constructed and shaped by cultural, historical, and social factors, rather than being objective and independent of human experience.

Hegel argued that the only way to achieve true knowledge is through the dialectical process of thesis, antithesis, and synthesis, in which opposing ideas are reconciled into a higher synthesis.

Linguistic Skepticism is the philosophical position that claims that knowledge is limited to what can be expressed in language, and that metaphysical and theological claims that cannot be expressed in language are meaningless.

René Descartes argued that the only way to achieve true knowledge is through the method of doubt, in which one systematically questions all beliefs until reaching indubitable foundations, such as the existence of the self ('I think, therefore I am').

Rationalism is the philosophical position that claims that knowledge is limited to what can be known through a priori reasoning, independent of sense experience, and that the mind contains innate ideas or principles that are self-evident and universally true.

Edmund Husserl argued that the only way to achieve true knowledge is through the method of phenomenological reduction, in which one brackets all assumptions and beliefs to focus on the pure essence of experience, revealing the structures of consciousness.