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Chapter 3

What Can We Know?

What is the Structure of the Cosmos?

• Anaximander: Proposed a spherical model of universe with the Earth at center; claimed that origin and guide of the cosmic process is Boundless force which creates and governs the world

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• Plato: Insisted that physical observable world is a poor copy of transcendent pure

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• Ideas that can be known only through reason.

What is the Structure of the Cosmos?

• Solomon: “There is nothing new under the Sun”; nothing really changes

• Parmenides: There is no motion or change; everything remains the same; all changes we suppose we observe are illusory

• Heraclitus: We “cannot step twice into the same river,” for everything is constantly changing; “nothing endures but change”

Skepticism

• Doubts our ability to answer metaphysical questions

• Argues against the possibility of real knowledge, whether gained by the sense or by reason

• Promoted by followers of Pyrrho of Elis– Because we can never attain certain

knowledge, our best path is to live quietly and modestly and seek peace of mind.

Epistemology

• Comprises the study of knowledge and the conditions for knowledge

• Term is based on the Greek word for knowledge, episteme

The Copernican Revolution

• Served as a powerful source of skepticism• Shattered the astronomical system of

Ptolemy which theorized that Earth is fixed, unmoving, and the sun orbits Earth

• In turn, collapsed the Aristotelian conception of physics that was wedded to the Ptolemaic system

• Was also in conflict with the Christian cosmology

Outcomes of theCopernican Revolution

• Our most cherished and obvious truths may in fact be false.

• Before we can draw a reliable observation about what we see, we must take into account the effects of our own observational position and faculties.

• Before we can ask what really exists, we must consider whether we have any legitimate and reliable method for knowing.

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René Descartes

1596-1650

Descartes

• Brought about major shift in how philosophy was done

• Profoundly influenced how we think about knowledge and the pursuit of knowledge

• Asked How can we know? (rather than What do we know?)

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Descartes in 3-Minutes

Descartes

• Turned to his own capacity for gaining knowledge (rather than the Church, the King, the Ancients)

• Insisted that if knowledge were to be gained, there would have to be a reliable method of gaining it

• Like other before him, believed that genuine knowledge must be certain

Descartes and Reason

• Descartes asserts that only the pure knowledge known by the resources of reason can be totally reliable.

• “Clear and Distinct Ideas”• Method of Doubt

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Discourse on the Method

1. “The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgment than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.”

2. “divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution.”

3. “conduct my thoughts in such order that, by commencing with objects the simplest and easiest to know, I might ascend by little and little, and, as it were, step by step, to the knowledge of the more complex”

4. “to make enumerations so complete, and reviews so general, that I might be assured that nothing was omitted."

Types of Knowledge

• A priori knowledge– Knowledge of pure reason, i.e. the truths

of mathematics and geometry– Knowledge that exists prior to experience

• A posteriori knowledge– Knowledge gained by (after) experience,

i.e. knowledge of the weather, or physics, or astronomy

Descartes’ Method of Doubt

• Begins by dismissing what most of us might regard as the best and most obvious candidates for indubitable truth

• Proposes a “malevolent demon” with awesome powers who devotes all his enormous skills and strengths to deceiving us

I Think, Therefore I Exist

• Descartes asserts that there is one bedrock certainty, an item of knowledge that each of us can confidently and assuredly know, no matter what some powerful deceiver uses against us.

• That absolutely certain and indubitable truth is: I exist, as a thinking thing— cogito, ergo sum.