Tripartite definition of sentential knowledge: Belief, truth, justification

Sentential knowledge is justified true belief.

When are we epistemically justified in accepting a statement? Four theories of justification:

+ Rationalism: From our reasoning powers

A proposition is said to be justified a priori if its epistemic justification (i.e.,the reason or warrant for thinking it to be true) does not depend on sensory experience.

Rationalists’ Critique of Empiricism: Empirical information (i.e., onethat is based on our physical senses) cannot be trusted because our senses can deceive us (e.g., mirages).

+ Empiricism: From empirical observations

A proposition is said to be justified a posteriori if its epistemic justification, the reason or warrant for thinking it to be true, depends on sensory experience.

Empiricists’ Critique of Rationalism: Ourreasoning ability is defective.  It can lead us astray (e.g., logical fallacies). Empiricists frown upon “arm-chair” approach to knowledge acquisition.

+ Transcendental Idealism: Combination of the above two theories; the form of our knowledge of reality derives from reason but its content comes from our senses

Kant called the world that our minds construct and that we seem to see around us the“phenomenal” world. The world as it might really be apart from our mind he called the “noumenal” world.

Kant’s revolutionary claim that the world must conform to the mind is often referred to as the Copernican revolution in knowledge. 

+ Skepticism: Knowledge has its limits; varies between doubting all assumptions until proved and claiming that no knowledge is possible

Many skeptics have restricted their skepticism to a particular domain of supposed knowledge: External world; Other minds; Past and future; Unperceived objects.