Epistemology

What do we know and how do we know it?

George MatthewsSpring 2016

What is knowledge?

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F We often think of knowledge as the opposite of belief.

F But since we must also believe what we know, knowledge isreally a type of belief that has something more than “merebelief.”

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F We often think of knowledge as the opposite of belief.

F But since we must also believe what we know, knowledge isreally a type of belief that has something more than “merebelief.”

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F To know something is to have a belief that is also true.

F Nobody really knew that the earth was flat – firmly heldbelief in a falsehood isn’t knowledge.

F There is a difference between thinking you know somethingand actually knowing it.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F To know something is to have a belief that is also true.

F Nobody really knew that the earth was flat – firmly heldbelief in a falsehood isn’t knowledge.

F There is a difference between thinking you know somethingand actually knowing it.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F To know something is to have a belief that is also true.

F Nobody really knew that the earth was flat – firmly heldbelief in a falsehood isn’t knowledge.

F There is a difference between thinking you know somethingand actually knowing it.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F Part of the difference involves having a good reason tobelieve what you claim to know.

F Thus we must also have a justification for a true belief tocount as knowledge.

F Lacking justifications our true beliefs would just be luckyguesses.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F Part of the difference involves having a good reason tobelieve what you claim to know.

F Thus we must also have a justification for a true belief tocount as knowledge.

F Lacking justifications our true beliefs would just be luckyguesses.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

F Part of the difference involves having a good reason tobelieve what you claim to know.

F Thus we must also have a justification for a true belief tocount as knowledge.

F Lacking justifications our true beliefs would just be luckyguesses.

What is knowledge?

To know something is to have a belief that is true and tohave a justification or good reason to believe it.

the standard definition

NOTE: defining knowledge in this way does notguarantee that we actually have any knowledge,it just sets a standard that we must meet inorder to legitimately claim to know something.

Plato’s Rationalism

Plato: 428 - 348 BCE

What we encounter in experience is animperfect manifestation of a more perfect

reality graspable by the mind alone.

Plato’s Rationalism

Plato: 428 - 348 BCE

If we see two square objects and conclude that theyare equal in size we must rely on concepts likeSQUARE and EQUALITY which we couldn’t pos-sibly have gotten from experience since no perfectsquares or exactly equal things exist in the world ofour experience.

Plato’s Rationalism

Plato: 428 - 348 BCE

The philosopher pursues wisdom by attempting tograsp these perfectly rational and ideal Forms mani-fest imperfectly in the world. Only after death will thesoul encounter such Forms directly, once it is freedfrom the limitations of the body.

Plato’s Rationalism

Plato: 428 - 348 BCE

For Plato learning is actually recollection ofideas of the Forms already imprinted on themind at birth.

Plato’s Rationalism

Plato: 428 - 348 BCE

Plato is a rationalist in that he thinks that reasontakes priority over experience in attaining knowledge.His views greatly influenced Christianity via the “neo-Platonists” who equated contemplation of the Plato’sForms with contemplation of the divine principle gov-erning the universe.

Descartes’ Rationalism

Rene Descartes: 1596 - 1650

We do not have direct experience ofreality but instead represent reality inour thoughts. The only guarantee that

these representations are accurate is someset of thoughts that cannot be doubted.

Descartes’ Rationalism

Rene Descartes: 1596 - 1650

Descartes relies on the method radical doubt to clearaway all ideas that are less than certain in search ofa sound foundation for knowledge.

Descartes’ Rationalism

Rene Descartes: 1596 - 1650

He is thus led to wonder how he can tell whether heis awake or dreaming or even completely deceived bya massive illusion. He finds that the only thing thatis certain is that as long as he is thinking or doubtinghe must exist – cogito ergo sum or “I think, thereforeI am.”

Descartes’ Rationalism

Rene Descartes: 1596 - 1650

But if he can be sure only that he himself exists, how can hefind a way out of solipsism, locked inside his own head un-certain of anything “outside”? To find a way out Descartesrelies on an argument that shows that a God exists whowould never let him be deceived as long as he relies onlyupon “clear and distinct ideas” as the basis for claims aboutthe world.

Descartes’ Rationalism

Rene Descartes: 1596 - 1650

But Descartes’ argument has struck many people asbeing circular. We rely on clear and distinct ideas toprove that God exists, but God’s existence is requiredfor us to be able to trust that clear and distinct ideasare in fact reliable.

Locke’s Empiricism

John Locke: 1632 - 1704

The mind at birth is a blank slate– experience is our sole sourceof knowledge about the world.

Locke’s Empiricism

John Locke: 1632 - 1704

Locke sets out to provide an account of the originsof all knowledge about the world, both particular andgeneral ideas, in direct experience. For Locke we startout knowing nothing and acquire all our knowledgethrough experience.

Locke’s Empiricism

John Locke: 1632 - 1704

Locke was arguing against those rationalist philosopherslike Descartes who claimed that we had certain “innateideas” built in to our minds. So he sets out to showhow even the most abstract ideas like SUBSTANCE arereally attained in experience.

Locke’s Empiricism

John Locke: 1632 - 1704

Many later philosophers felt that Locke’s attempts to showhow abstract concepts were derived from experience did notreally work. For rationalists his argument assumes that wealready know what these concepts mean, while for empiri-cists, they remain too abstract to really have been derivedfrom experience.

Berkeley’s Idealism

George Berkeley: 1685 - 1753

To be is tobe perceived.

Berkeley’s Idealism

George Berkeley: 1685 - 1753

Berkeley defends a rather strange sounding claim, thatsince we cannot make sense of what something would belike without actually perceiving it or imagining that we aredoing so, we should stop assuming that anything can havean existence apart from being apprehended by some mind.

Berkeley’s Idealism

George Berkeley: 1685 - 1753

On this view a tree falling in the forest with no onearound to witness it not only doesn’t make a sound,it doesn’t even exist.

Berkeley’s Idealism

George Berkeley: 1685 - 1753

By why then do things seem to persist in betweentimes we perceive them? Berkeley answers that theremust be a mind perceiving things to keep them in thesame state from one moment to the next and thismind is the mind of God.

Berkeley’s Idealism

George Berkeley: 1685 - 1753

Berkeley is led to this extreme conclusion by thinking throughthe basic empiricist idea that our knowledge comes from ourexperience alone – outside of experience we can say nothingabout objects, hence objects that are not objects of someone’sexperience are meaningless.

Hume’s Skeptical Empiricism

David Hume: 1711 - 1776

All of our knowledge claims are either claimsabout ideas and their definitions, or claimsabout particular experiences. So generalizing

about experience is always hazardous.

Hume’s Skeptical Empiricism

David Hume: 1711 - 1776

Hume was interested in applying the scientific method tothe study of human beings and was thus the first mod-ern cognitive psychologist. Today he is most known forhis skepticism about abstract concepts like CAUSATION,SUBSTANCE and SELF.

Hume’s Skeptical Empiricism

David Hume: 1711 - 1776

For Hume all concepts we use to talk about what we experi-ence should themselves be based on direct experiences. But,with causality for example, we never actually experience onething causing another, instead we see one thing happen andthen another. So we should give up the general idea of cau-sation in his view.

Hume’s Skeptical Empiricism

David Hume: 1711 - 1776

Likewise with the concept of a SELF or soul underlying andunifying our experiences and our personalities. Each of usexperiences a series of particular events, but never do weencounter a SELF or soul having those experiences.

Hume’s Skeptical Empiricism

David Hume: 1711 - 1776

Hume’s epistemology is based on his claim that all knowledgemust either be a matter of the definitions of words or directexperiences. But is this claim itself something he knows bydefinition or that he could have gotten from experience? Itseems to be neither, so how can Hume claim that it is true?

Kant’s Constructivism

Immanuel Kant: 1724 - 1804

Instead of assuming that ourknowledge must conform to objects,we should suppose that objects mustconform to our cognitive powers.

Kant’s Constructivism

Immanuel Kant: 1724 - 1804

Kant responded to the debate between the empiricistsand the rationalists by saying that both were right incertain ways and both wrong in other ways.

Kant’s Constructivism

Immanuel Kant: 1724 - 1804

The empiricists were right in that the content of our knowledgeabout the world certainly comes from experience. In addition,the fact that philosophers get caught in endless debates aboutfreedom, immortality, the soul, God, whether the world is finiteor infinite, shows that our knowledge cannot extend beyondwhat we are capable of experiencing.

Kant’s Constructivism

Immanuel Kant: 1724 - 1804

The rationalists, however, were right in that the mind providesan a priori structure to experience. The general concepts weuse to organize and make sense of experience are built in tothe mind. Hence we cannot help by see one thing as causinganother, a unified world of things organized in space and time,and possessing an internal identity that allows them to persistthrough time.

Kant’s Constructivism

Immanuel Kant: 1724 - 1804

Kant’s conception of knowledge as a combination of empiricalcontent and a priori structure has been central to all post-Kantian philosophy and the field of cognitive psychology. Thebig question is whether this structure is universal and commonto all rational beings, as Kant thought, or variable amongdifferent cultures, genders or even individuals. Maybe there isa bit of both – perhaps we all share certain basic concepts,but then other aspects of our experience are variable.