Aporia - Aporia is the Greek term for the state of helplessness—the inability to
proceed—that ends all of Plato’s early dialogues. Through his pointed questioning,
Socrates succeeds in showing that his interlocutors have no appropriate definition for
the topic under consideration (be that topic piety, love, courage, justice, or whatever
else), but nor is he able to supply one himself. In Book I of The Republic Socrates
brings his friends to a state of aporia on the topic of justice, but then in the next nine
books he manages to move beyond the aporia and give an actual answer to the
question at hand.
Appetite - Appetite is the largest aspect of our tripartite soul. It is the seat of all our
various desires for food, drink, sexual gratification, and other such pleasures. It
contains both necessary desires, which should be indulged (such as the desire to eat
enough to stay alive), unnecessary desires, which should be limited (such as the desire
to eat a ten pound sirloin steak at every meal), and unlawful desires, which should be
suppressed at all costs (such as the desire to eat one’s children). Though the appetite
lusts after many things, Plato dubs it “money-loving,” since money is required for
satisfying most of these desires. In a just man, the appetite is strictly controlled by
reason and reason’s henchman, spirit.
Auxiliary - Plato divides his just society into three classes: the producers, the
auxiliaries, and the guardians. The auxiliaries are the warriors, responsible for
defending the city from invaders, and for keeping the peace at home. They must
enforce the convictions of the guardians, and ensure that the producers obey.
Belief - Belief is the second lowest grade of cognitive activity. The object of belief is
the visible realm rather than the intelligible realm. A man in a state of belief does not
have any access to the Forms, but instead takes sensible particulars as the most real
Elenchus - Elenchus is the Greek term for Socrates’s method of questioning his
interlocutors. In an elenchus he attempts to show that their own beliefs are
contradictory, and thus to prove that they do not have knowledge about some topic
about which they thought they had knowledge.
Empirical - When something is an empirical question, that means that the question
can only be settled by going out into the world and investigating. The question, “What
percentage of the population of the United States likes ice cream” is an example of an
empirical question, which can only be answered through empirical investigation. The
question “What is the square root of two,” on the other hand, is not an empirical
question. In order to answer this question all you have to do is think about the
mathematics involved; you do not have investigate evidence in the world.
Epistemology - The branch of philosophy concerned with knowledge, belief, and
thought. Epistemological questions include: What is knowledge? How do we form
beliefs based on evidence? Can we know anything?
Form - According to Plato’s metaphysical theory, there is an aspect of reality beyond
the one which we can see, an aspect of reality even more real than the one we see.
This aspect of reality, the intelligible realm, is comprised of unchanging, eternal,
absolute entities, which are called “Forms.” These absolute entities—such as
Goodness, Beauty, Redness, Sourness, and so on—are the cause of all the objects we
experience around us in the visible realm. An apple is red and sweet, for instance,
because it participates in the Form of Redness and the Form of Sweetness. A woman
1 is beautiful because she participates in the Form of Beauty. Only the Forms can be
objects of knowledge (that is, Forms are the only things we can know about).
Form of the Good - Among the Forms, one stands out as most important. This is the
Form of the Good. Plato is unable to tell us exactly what the Form of The Good is, but
he does tell us that it is the source of intelligibility and of our capacity to know, and
also that it is responsible for bringing all of the other Forms into existence. He
compares its role in the intelligible realm to the role of the sun in the visible realm.
The Form of the Good is the ultimate object of knowledge; it is only once one grasps
the Form of the Good that one reaches the highest grade of cognitive activity,
understanding. Therefore, it is only after he grasps the Form of the Good that a
philosopher-in-training becomes a philosopher-king.
Guardian - Plato divides his just society into three classes: the producers, the
auxiliaries, and the guardians. The guardians are responsible for ruling the city. They
are chosen from among the ranks of the auxiliaries, and are also known as
Hesiod - Hesiod was a famous Greek poet. His long poem Works and Daysoutlines
the traditional Greek conception of virtue and justice.
Imagination - Imagination is the lowest grade of cognitive activity. Someone in the
state of imagination takes mere images and shadows as the most real things. Probably,
this means that such a person derives his ideas about himself and the world from
products of art, such as poetry in Plato’s day and movies and television in our own.
See also Belief, Thought, Understanding.
Instrumental reason - Instrumental reason is reason used to attain some end, by
engaging in means-end analyses. These ends are dictated by a part of the soul such as
appetite or spirit, or even reason itself.
Intelligible realm - Plato divides all of existence up into two parts: the visible realm
and the intelligible realm. The intelligible realm cannot be sensed, but only grasped
with the intellect. It consists of the Forms. Only the intelligible realm can be the
object of knowledge.
Kallipolis - Kallipolis is the Greek term for Plato’s just city.
Knowledge - According to Plato, knowledge can only pertain to eternal, unchanging
truths. I can know, for instance that two plus two equals four, because this will also be
the case. I cannot know, however, that Meno is beautiful. For this reason, only the
intelligible realm, the realm of the Forms can be the object of knowledge. See also
Lover of sights and sounds - “Lovers of sights and sounds” is Socrates’s term for
the pseudo-intellectuals who claim to have expertise regarding all that is beautiful, but
who fail to recognize that there is such a thing as the Form of the Beautiful, which
causes all beauty in the visible realm. Socrates is adamant that lovers of sights and
sounds be distinguished from philosophers, who grasp the Forms, and thus have
knowledge. Lovers of sights and sounds have no knowledge, only opinion.
Metaphysics - The branch of philosophy concerned with asking what there is in the
world. The theory of Forms is a metaphysical theory, as is the theory of the tripartite
Opinion - Since only eternal, unchanging truths can be the objects of knowledge, all
other truths are relegated to opinion. Opinion is the highest form of certainty that we
can hope for when it comes to the visible realm, the realm of sensible particulars.
Philosopher-king - The philosopher-king is the ruler of the kallipolis. Also called
guardians, philosopher-kings are the only people who can grasp the Forms, and thus
2 the only people who can claim actual knowledge. Since the philosopher-king yearns
after truth above all else, he is also the most just man.
Pleonexia - A Greek term meaning “the desire to have more,” pleonexiarefers to the
yearning after money and power. In Book I, Thrasymachus presents the popular view
that justice is nothing more than an unnatural restraint on our natural pleonexia.
Producers - Plato divides his just society into three classes: the producers, the
auxiliaries, and the guardians. The producing class is the largest class of society; it is
a catch-all group that includes all professions other than warrior and ruler. Framers
and craftsmen are producers, as are merchants, doctors, artists, actors, lawyers,
judges, and so forth. In a just society, the producers have no share in ruling, but
merely obey what the rulers decree. They focus exclusively on producing whatever it
is that they are best suited to produce (whether that be metal work, agriculture, shoes,
Reason - Reason is one aspect of our tripartite soul. It lusts after truth and is the
source of all of our philosophic desires. In the just man, the entire soul is ruled by
reason, and strives to fulfill reason’s desires. See also Appetite, Spirit.
Sensible particular - Sensible particulars are the objects that we experience all
around us—trees, flowers, chairs—any physical objects. They are “sensible” because
we can sense them with our sight, smell, hearing, taste, and touch; they are
“particular,” because they are particular items that undergo change over time, rather
than universal, unchanging ideas. According to Plato’s metaphysical picture, the
visible realm is made up of sensible particulars. According to his epistemological
picture, sensible particulars cannot be objects of knowledge but only of opinion.
Sophist - The Sophists were teachers-for-hire who educated the wealthy men of
Athens in the fifth century B.C. Though they were a diverse group with diverse
opinions, they tended to share a disregard for the notion of objective truth and
knowledge. This disregard extended to the notion of objective moral truth, which
means that they did not believe in such a things as “right” and “wrong.” One of the
guiding motivations in all of Plato’s work was to prove the Sophists wrong: to show
that there is such a thing as objective truth, and that we can have knowledge of this
Specialization - The principle of specialization states that every man must fulfill the
societal role to which nature best suits him, and should refrain from engaging in any
other business. Those naturally suited to farm should farm, those naturally suited to
heal should be doctors, those naturally suited to fight should be warriors, those
naturally suited to be philosophers should rule, and so on. Plato believes that this
simple rule is the guiding principle of society, and the source of political justice.
Spirit - Spirit is one aspect of our tripartite soul. It is the source of our honor-loving
and victory-loving desires. Spirit is responsible for our feelings of anger and
indignation. In a just soul, spirit acts as henchman to reason, ensuring that appetite
adheres to reason’s commands.
Thought - Thought is the second highest grade of cognitive activity. As with
understanding, the objects of thought are the Forms of the intelligible realm. Unlike
understanding, though, thought can only proceed with the crutches of images and
hypotheses (i.e. unproven assumptions). See also Belief, Imagination, Understanding.
Tripartite soul - According to Plato, the human soul has three parts corresponding
to the three classes of society in a just city. Individual justice consists in maintaining
these three parts in the correct power relationships, with reason ruling, spirit aiding
reason, and appetite obeying.
3 Understanding - Understanding is the highest grade of cognitive activity.
Understanding involves the use of pure, abstract reason, and does not rely on the
crutches of images and unproven assumptions. Understanding is only achieved once
the Form of the Good is grasped. See also Belief, Imagination, Thought.
Visible realm - Plato divides existence up into two realms, the visible realm and the
intelligible realm. The visible realm can be grasped with our senses. It is comprised of
the world see around us—the world of sensible particulars. The objects which
comprise the visible realm are not as real as those which comprise the intelligible
realm; in addition, they are not the proper objects of knowledge (i.e., we cannot
“know” anything about them), but of opinion.
Glossary of terms (plus objections) for Descartes’ Meditations
The theory of knowledge – what it is and how we can secure it
The idea that no knowledge is secure and that doubt is inevitable. In Descartes’ time
people were sceptical about religious knowledge and scientific knowledge.
To combat the sceptics, Descartes used their own method: doubting everything he
could to try and discover knowledge which was secure.
The idea that knowledge must rest on a secure foundation. Mathematical knowledge
is an example: it rests on axioms (self-evident, intuitively true propositions) and
discovers new knowledge by employing self-evidently true operations (such as the
Law of Equality where if you have an equation, adding (or subtracting etc.) anything
to one side as well as the other maintains equality). Foundationalists hold that all
knowledge must be like this.
The position that claims knowledge is primarily gained through thought.
The position that claims that knowledge is primarily gained through our senses.
Descartes thought this position wrong (he is a rationalist) arguing that our senses are
not totally reliable and so cannot deliver reliable knowledge.
A particular piece of knowledge delivered by the senses e.g. the red pen, the taste of
Descartes’ puts an empiricist objection: surely I can know my own body exists? Well
no, he answers, in dreams I appear to myself to be experiencing a ‘physical world’ but
we know that there is not really such a physical world in dreams – so it is possible that
I am now dreaming the ‘real waking world’ In that case, he lets the empiricist reply,
even if the physical world does not really exist, that I am dreaming it exists, the fact
that my ‘dream’ is crowded with objects implies (in the philosophical sense) that such
objects must also exist somewhere outside my mind. Descartes replies that we cannot
be so sure: in our dreams we concoct “sirens and satyrs” i.e. objects which are false.
Finally, the empiricist can say that the sirens and satyrs are composed of components
which cannot have been made up by my mind (the ‘Simples’), so implying they exist
4 Descartes’ Simples
The basic components which seem to be impossible to synthesise in the mind –
including colour, extension, shape, mass, size, number, time.
Evil Demon Argument
His final strike against the empiricist and, indeed, against those thinking mathematical
knowledge secure: even the ‘Simples’ might be false knowledge being fed into the
mind by an evil demon (or ‘malign spirit’) together with a sense of certainty. Even
though in dreams “2 + 3 = 5 and a quadrilateral figure has no more than 4 sides” the
demon could vary these ‘truths’.
He points out that certainty is not the same as truth. Mad people (who “claim to be
kings”, “have an earthenware head”, “are made of glass”) are certain that they know
‘truths’ which we know to be false.
• He gives no explanation or justification for the claim that all knowledge must
be foundational in character. Scientific knowledge is as secure as we could
wish but we know it is not foundational: it is based on theories which, by their
nature, are provisional.
• It is incoherent to jettison all beliefs as he recommends (like emptying all the
apples from a basket and then replacing the sound ones). We need some
beliefs to allow us to judge other beliefs – they can’t all be jettisoned.
To his rejection of empirical knowledge
• False empirical knowledge is capable of being corrected (as Descartes himself
says when he relates how a distant tower appears round but, closer to, turns
out to be square) by ‘better’ empirical knowledge. The ‘counterfeit coins’
argument is an analogy: just as false coins are only possible if there are true
ones around for comparison, false sense-data are only possible if there are true
sense-data around for comparison. All empiricists have to do is ensure they
are careful to work with the true ones rather than the false.
Descartes could reply to this latter objection by saying that he’s after total certainty
(because he is a foundationalist rather than someone like today’s scientific society
happy with the security of scientific knowledge) which cannot be delivered by sense-
experience: just as even an expert cannot know for certain a particular coin is genuine,
we cannot know for certain which are our ‘true’ sense-data.
Fixed locus from which the Earth itself can be moved: secure foundation.
Cogito ergo sum
It is logically impossible to doubt one is thinking (since a doubt is itself a thought).
This is proof against even the evil demon and provides a point of certainty: whenever
I am thinking, I must exist.
5 This argument establishes the primacy of the subject (the individual mind) in
knowledge, i.e. rationalism is the route to true knowledge – so upsetting those who
believe that objective (empirical) knowledge is primary.
The belief that that there are two substances in the world: physi