1. Rationalism: Knowledge Is Acquired through Reason, not the Senses We know only that of which we are certain. Sense experience cannot guarantee certainty, so all that we know comes from reason alone and is a priori (i.e., prior to experience) Our (innate) knowledge of certain propositions is based on remembering truths acquired before birth Plato (427-347 BCE)

2. Empiricism: Knowledge about the World Is A Posteriori (Based on Experience Alone) At birth the mind is a blank slate (tabula rasa), containing no innate ideas. Even if some ideas were known universally, that does not prove they are innate Knowledge comes from sensation or reflection Ideas of “primary qualities” (e.g., solidity, shape) represent things as they really are; ideas of secondary qualities (e.g., colors) represent things only as they appear to us John Locke (1632-1704)

3. Naïve Realism: We Do Not Perceive Ideas; We Perceive Their Objects Perceptions are always “intentional,” that is, about something; and when our perceptions are caused by the things they are about, we can be said to know those things Perceptions are not purely passive; they are affected by one’s background knowledge and beliefs John Searle

4. Analytic and Synthetic Judgments Hume: propositions are either relations of ideas (analytic, a priori) or matters of fact (synthetic, a posteriori) Kant: propositions in mathematics (7+5=12) and metaphysics (“all events have causes”) are synthetic a priori judgments Quine: meanings of terms in even a priori analytic propositions depend on experience David Hume Immanuel Kant (1724-1804)