Unit 3: Theories of Knowledge

Theories of Knowledge: Introduction

This unit deals with Epistemology, the theory of knowledge. The central debate in "modern" philosophy (17th-18th centuries) was between Rationalism and Empiricism. They are competing answers to the question: "What is the primary source of human knowledge?"

Rationalism

Rationalism is the epistemological view that reason is the chief source and test of knowledge. Rationalists believe that, in addition to sense experience, we possess "innate ideas" or *a priori* (non-experiential) knowledge. True knowledge is certain, and this certainty can only come from mathematical or logical deduction, not from the unreliable senses.

Key Proponents:

1. René Descartes (1596-1650):
   • Method of Doubt: He doubted everything he could (senses, dreams, even math) to find an indubitable foundation for knowledge.
   • "Cogito, Ergo Sum": ("I think, therefore I am.") The one thing he could not doubt was his own existence as a "thinking thing."
   • Innate Ideas: From this single certainty, he used reason to "prove" the existence of God (whom he argued is perfect and not a deceiver) and the external world. The idea of God, infinity, and perfection are innate (in-born).
2. Baruch Spinoza (1632-1677): Built a complete metaphysical system based on logical-geometric deduction, starting from a few self-evident axioms (like in Euclid's geometry).
3. Gottfried Wilhelm Leibniz (1646-1716): Argued for the "Principle of Sufficient Reason" (nothing is without a reason) and a pre-established harmony between "monads" (simple substances).

Motto: "The senses can be deceptive. True knowledge comes from pure reason, like in mathematics." (e.g., 2 + 2 = 4 is true without needing to check it in the world).

Empiricism

Empiricism is the epistemological view that sense experience is the primary, or even the *only*, source of knowledge. Empiricists reject the concept of "innate ideas." They argue the mind at birth is a tabula rasa (a "blank slate").

Key Proponents:

1. John Locke (1632-1704):
   • Tabula Rasa: The mind is a blank slate, and all ideas come from experience.
   • Two Sources of Ideas:
     1. Sensation: Ideas from external objects (e.g., "yellow," "hot").
     2. Reflection: Ideas from our own mind's operations (e.g., "thinking," "doubting").
   • Primary vs. Secondary Qualities: Primary qualities (size, shape) exist *in* the object. Secondary qualities (color, taste) are powers in the object to produce sensations *in us*.
2. George Berkeley (1685-1753): A more radical empiricist. He rejected Locke's "matter" and primary qualities, arguing that *all* qualities are mind-dependent. (Covered in Unit 4).
3. David Hume (1711-1776): The most radical empiricist. He argued that if all knowledge comes from experience, we cannot have knowledge of "causality" or "substance," as we never *experience* them directly. (Covered in Unit 5).

Motto: "Nothing is in the intellect that was not first in the senses." (Nihil in intellectu quod non prius in sensu).

Exam Tip: This is a classic "compare and contrast" question.

Feature	Rationalism (Descartes)	Empiricism (Locke)
Source of Knowledge	Reason & Innate Ideas	Sense Experience
Mind at Birth	Contains innate ideas (e.g., God)	Tabula Rasa (Blank Slate)
Model for Knowledge	Mathematics (Deduction)	Natural Science (Induction)
Role of Senses	Unreliable, source of confusion.	The only source of data.