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Idea (Greek: Template:Polytonic, from eidon: "I saw" ) in classical Greek it usually meant the visual aspect of something.

• Latin: "look, form," from idein "to see," eidenai "to know"; where oid is suffix for "like, likeness, like that of"
• Greek: -oeides, from eidos for "image", "form", "shape", "appearance", "semblance", "structure", "morph"
• PIE: wid-es-ya-, suffixed form of base weid- "to see" and in perfect verb stem "to know" (wit, wise, wisdom)

The word idea was recorded circa 1430 meaning, "figure, image, symbol." The concept for the use of the word as related to "as a result of thinking" was first recorded around 1645. The human capacity to contemplate ideas is associated with the capacity for reason, self-reflection, and the ability to acquire knowledge and apply intellect. Ideas give rise to concepts, which are the basis for any kind of knowledge whether science or philosophy. However, in a popular sense, an idea can arise even when there is no serious reflection, for example, when we talk about the idea of a person or a place. From the aspect of an "image" very often visual shape is primarily involved. The transferred sense of type or kind springs quite naturally from this use. Thus Thucydides writes of "many ideas (kind) of warfare." (History of the Peloponnesian War Book I, 109). Clement of Alexandria simply defines an idea as "a thought of God". The ideas are still perfect and eternal exemplars, but now they are in the mind of God. The term idea could then be taken to cover patterns, blueprints, or plans in anybody's mind, including a diety or demiurge. Thomas Aquinas says that "the word idea signifies a certain form thought of by an agent in the likeness of which he intends to produce an external work (Quaestionses Quodlibetales IV, I, Ic)." Rudolph Goclenius says "that in general an idea is a form or exemplar of a thing with an eye on which a workman makes what he has planned in his mind (Philosophicum 208a)." The original meaning of the term form (Greek and Latin) was and is that in common use — eidos (derived from eido, root rid, an obsolete form from which comes the second aorist eidon (I see), akin to Latin video (that which is seen), with secondary meanings derived from this, as form, sort, particular, kind,and nature.

Philosophy

In philosophy, the term idea is common to all languages and periods, but there is scarcely any term which has been used with so many different shades of meaning. The view that ideas exist in a realm separate or distinct from real life is one theme in philosophy, referred to as innate ideas. Another view holds that we only discover ideas in the same way that we discover the real world, from personal experiences. The view that humans acquire all or almost all their behavioral traits from nurture (life experiences) is known as tabula rasa ("blank slate"). Most of the confusions in the way of ideas arise at least in part from the use of the term idea to cover both the representation percept and the object of conceptual thought. This can be illustrated in terms of the doctrines of innate ideas, "concrete ideas verses abstract ideas", as well as "simple ideas verses complex ideas".

The term noetic (from nous) pertains to activity of the mind: in forming ideas, the application of thought, intuitive reason, and intellect. An intellectual is one who tries to use their intellect to work, study, reflect, speculate on, and answer questions with regard to a variety of different ideas. Aristotle asserted that nous was the intellect and in the Pre-Socratics nous became increasingly identified with practical knowledge and reason as opposed to perception. Among philosophers like Plato and Aristotle, who were concerned with the relationship between the soul and body, an analogous belief in the primacy and independence of the intellectual faculty persists¹. Aristotle defines soul as "the primary actuality of a natural body which potentially has life" (De anima 412a 27-28). The influence of Plato was strong enough to make Aristotle regard mind (nous) as a faculty of the soul which has no physical base and which may be capable of existing outside the body². Nous is from the beginning intellective or cognitive, expressive to see and to know. Plato would appear to have been the first to relate the two by locating, as he does ³, nous within the soul both in the macrocosm and the microcosm.

Homer's concept of nous was a representation of intellect, reason, and practical ideas (common sense). Nous is his favorite word to describe "mental seeing" or images in the mind. The faculties by which we apprehend the noeton, "the intelligible world" are two: nous, "intuitive reason", which reaches the ideas; and logos, "discursive reason", which by its proper process, viz. episteme "demonstration", attains only to dianoia "conception". The Stoics equated nous with the logos, so that for them it was both the cosmic reason and the rational element in man. The central Stoic idea of logos strongly influenced Christian theology, in particular of identifying Christ (Iesous) with the logos (see John 1 and the Gospel). To the Platonists the divine being is the "the cosmic soul" (cosmic reason) which contains the human reason (nous - common sense) as one of the emanations of the ideas from God. Some versions of the Platonic realism regard Plato's forms as ideas in the mind of God. Due to the potential confusion of the term idea, philosophers usually use the terms form, Platonic form, or universal. The words idea , weid, eidos, and nous come from the Indo-European languages. The name Iesous (pronounced "ee-yay-soos" or "e-ay-sous") is from Greek.

Plato

Plato utilized the concept of idea in the realm of metaphysics. The core of his philosophy is the doctrine of ideas. He asserted that there is a realm of ideas in his Theory of Forms, which exist independently of anyone who may have thought of these ideas. Form and idea are used interchangeably to designate that which remains the same through all the manifestations of a material thing or a virtue. Material things are then imperfect and transient reflections or instantiations of the perfect and unchanging ideas. To Plato an idea is something outside the mind. He posited a realm of truth (supreme being) in which ideas reside. This is contrary to world of opinion called Doxa. Plato's concept was that through the soul, the mediator between the ideas and appearances, we may obtain knowledge.

From this it follows that these ideas are the principal reality (see idealism); opposed to this form of idealism are empirical thinkers of various times who find reality in particular physical objects (see hylozoism, empiricism). In his more technical use, the ideas and forms are always spoken of as:

1. the objects of intelligence, in contrast with objeects of perception
2. things which truly are, in contrast with changing objects of perception, which are in a state of becoming
3. eternal, in contrast with the persihable world of change.

Plato described ideas as the immortal, rational part of the soul. He describes the soul of the world as the component that brings reasoned order to the universe. It is a godlike kind of thinking in which the truths of conclusions are immediately known without having to understand the preliminary premises. It is the theory of Ideas as separate and eternal paradigms that appear in the Timaeus. There the divine demiurge is depicted as forming the world on the pattern of the eternal Forms. Greek διFος ("divine") is descended from deiwos, from the same root as Dyēus. Plato describes The Idea of the Good in his book, The Republic. The Platonic Idea of the Good is the offspring (ekgonos) of the Good; the ideal or perfect nature of goodness, and so an absolute measure of justice. He said that this was the highest form of knowledge from which things gain their usefulness and value. Humans have a duty to pursue the good. The Idea of the Good was identified with God by St Augustine. Plato's "Idea of the Good" is the counterpart of the Nous of Anaxagoras (one of Plato's predecessors).

Saint Augustine

Augustine was the outstanding figure in philosophy between the time of Plato and Thomas Aquinas, a period of 1600 years. He introduced the fusion of Platonism and Christianity. One thing that made it possible for Augustine to fuse the Platonic tradition in philosophy with Christianity is the fact that the later is not a philosophy, but rather of historical beliefs. The basic idea of Catholic Christianity is that God made our world and then came to live in it through Iesous. Jesus of Nazareth lived in a particular part of the world called Palestine, at a particular time (some 2000 years ago), and lived a particular historical course. Being a Christian involves believing this as well as live a way that God told us to through the Word of this entity. While this Word did provide us with a good deal of moral instruction, it was not much in discussing philosophical questions. In the Platonic tradition ideas are more real than things. Plato developed a vision of two worlds: a world of unchanging ideas and a world of changing physical objects (i.e. the experience of the historical Jesus). It was not the case that there was a Platonic philosophy and on the other hand the Christian philosophy - thus giving Augustine the problem of marrying the two. It was closer to the idea that Christianity was not a philosophical religion like Buddhism and Augustine believed that the Platonic philosophy embodied important truths about aspects of reality that the Bible did not concern itself with. He wanted Platonism to be absorbed into the word wide Christian view. Augustine realized it was important not to take on board any particular aspect of Platonism that might have as one of its logical consequences something that contradicted Christianity. At that time Christianity was considered the self revelation of God. It was believed by Christians that any idea in contradiction to the Christian faith was heresy. Augustine knew that any new ideas were always dictated by prior claim to the truth by Christianity. He saw new philosophical ideas as playing a secondary role to the religious revelation. Nonetheless he was successful in his aim of getting Platonic ideas absorbed into the church's view of the nature of reality.

Francesco Petrarch

Petrarch, founder of Renaissance humanism, was the originator of a new interest in Plato's ideas and Platonism where they were borne again starting in the fourteenth century due to his efforts. The idea of a revival or rebirth of culture after the barbarism of the Dark Ages (a term coined by Petrarch) was a favorite notion of the humanists. The references to Plato which Petrarch discovered personally in letters of Cicero led him to proclaim Plato's superiority to Aristotle. Petrarch even declared to four Venetian critics that he possessed a lost manuscript of sixteen dialogues by Plato of these ancient ideas. It was seen that the Plato ideas throughout the Renaissance were a newly discovered pre-Christian sage whose exciting doctrines, wrapped in esoteric mythology, challenged the cut and dry teachings of Aristotle. Platonism played a major role throughout the Renaissance from the time of its introduction by Petrarch as a countervailing force against the traditional Aristotelian teachings. Petrarch's Canzoniere was the most influential lyric poetry of all time with Augustinian Platonism. Platonism and Petrarchism walked hand in hand throughout the Renaissance.

Ideas, which are transcendent universals, alone constitute reality as against the shadowy existence of particular material objects. Chief among these ideas is the Idea of the Good. This was seen as supreme both as the goal of knowledge and as the guide to morality. Petrarch followed Plato's idea that the only real knowledge was the knowledge of ideas. It was pictured mythically as a sort of reminiscence of the transmigrated soul's earlier existence. The Christianizing tendency of Renaissance Platonists with its ideas of the Platonic idealism is seen in Petrarch when he says, "Of Plato, Augustine does not in the least doubt that he would have become a Christian if he had come to life again in Augustine's time or had foreseen the future while he lived. Augustine relates also that in his time most of the Platonists had become Christians and he himself can be supposed to belong to their number." Petrarch wrote a personal book called Secretum which was about the Idea of the Good as related to his moral ideals in imaginary discussions with Augustine.

René Descartes

Descartes often wrote of the meaning of idea as an image or representation, often but not necessarily "in the mind", which was well known in the vernacular. In spite of the fact that Descartes is usually credited with the invention of the non-Platonic use of the term, we find him at first following this vernacular use. In his Meditations on First Philosophy he says, "Some of my thoughts are like images of things, and it is to these alone that the name 'idea' properly belongs." He sometimes maintained that ideas were innate and uses of the term idea diverge from the original primary scholastic use. He provides multiple non-equivalent definitions of the term, uses it to refer to as many as six distinct kinds of entities, and divides ideas inconsistently into various genetic categories. For him knowledge took the form of ideas and philosophical investigation is the deep consideration of these ideas. Many times however his thoughts of knowledge and ideas were like those of Plotinus and Neoplatonism. In Neoplatonism the Intelligence (Nous) is the true first principle -- the determinate, referential 'foundation' (arkhe) -- of all existents; for it is not a self-sufficient entity like the One, but rather possesses the ability or capacity to contemplate both the One, as its prior, as well as its own thoughts, which Plotinus identifies with the Platonic Ideas or Forms (eide). A non-philosophical definition of Nous is good sense (a.k.a. "common sense"). Descartes is quoted as saying, "Of all things, good sense is the most fairly distributed: everyone thinks he is so well supplied with it that even those who are the hardest to satisfy in every other respect never desire more of it than they already have."

John Locke

In striking contrast to Plato’s use of idea is that of John Locke in his masterpiece Essay Concerning Human Understanding in the Introduction where he defines idea as "It being that term which, I think, serves best to stand for whatsoever is the object of the understanding when a man thinks, I have used it to express whatever is meant by phantasm, notion, species, or whatever it is which the mind can be employed about in thinking ; and I could not avoid frequently using it." He said he regarded the book necessary to examine our own abilities and see what objects our understandings were, or were not, fitted to deal with. In his philosophy other outstanding figures followed in his footsteps - Hume and Kant in the 18th century, Arthur Schopenhauer in the 19th century, and Bertrand Russell, Ludwig Wittgenstein, and Karl Popper in the 20th century. Locke always believed in good sense - not pushing things to extremes and on taking fully into account the plain facts of the matter. He considered his common sense ideas "good-tempered, moderate, and down-to-earth."

David Hume

Hume differs from Locke by limiting "idea" to the more or less vague mental reconstructions of perceptions, the perceptual process being described as an "impression." Hume shared with Locke the basic empiricist premise that it is only from life experiences (whether our own or other's) that out knowledge of the existence of anything outside of ourselves can be ultimately derived. We shall carry on doing what we are prompted to do by our emotional drives of all kinds. In choosing the means to those ends we shall follow our accustomed association of ideas. Hume is quoted as saying: "Reason is the slave of the passions."

Immanuel Kant

Immanuel Kant defines an "idea" as opposed to a "concept". "Regulator ideas" are ideals that one must tend towards, but by definition may not be completely realized. Liberty, according to Kant, is an idea. The autonomy of the rational and universal subject is opposed to the determinism of the empirical subject. Kant felt that it is precisely in knowing its limits that philosophy exists. The business of philosophy he thought was not to give rules, but to analyze the private judgements of good common sense.

Rudolf Steiner

Whereas Kant declares limits to knowledge ("we can never know the thing in itself"), in his epistemological work, Rudolf Steiner sees ideas as "objects of experience" which the mind apprehends, much as the eye apprehends light. In "Goethean Science" (1883), he declares, "Thinking… is no more and no less an organ of perception than the eye or ear. Just as the eye perceives colors and the ear sounds, so thinking perceives ideas." He holds this to be the premise upon which Goethe made his natural-scientific observations.

Wilhelm Wundt

Wundt widens the term from Kant's usage to include conscious representation of some object or process of the external world. In so doing, he includes not only ideas of memory and imagination, but also perceptual processes, whereas other psychologists confine the term to the first two groups. One of Wundt's main concerns was to investigate conscious processes in their own context by experiment and introspection. He regarded both of these as exact methods, interrelated in that experimentation created optimal conditions for introspection. Where the experimental method failed, he turned to other objectively valuable aids, specifically to those products of cultural communal life which lead one to infer particular mental motives. Outstanding among these are speech, myth, and social custom. Wundt designed the basic mental activity apperception - a unifying function which should be understood as an activity of the will. Many aspects of his empirical physiological psychology are used today. One is his principles of mutually enhanced contrasts and of assimilation and dissimilation (i.e. in color and form perception and his advocacy of objective methods of expression and of recording results, especially in language. Another is the principle of heterogony of ends - that multiply motivated acts lead to unintended side effects which in turn become motives for new actions.

Charles Sanders Peirce

According to the 1911 Encyclopedia Britannia, C. S. Peirce is now recognized as the most original and the most versatile intellect that the Americas have so far produced. By the age of 48 he had devoted himself entirely to philosophy. He never wrote a book and most of his publications were posthumous works. His central contention was that knowledge is an activity. The application of intelligence is primarily evaluative and is aimed at achieving understanding. He contended that knowledge consists of valid reasonable explanations and solutions to our problem-situation. He published many papers on this logic. He also published the first full statement of pragmatism which was his first important work of How to Make Our Ideas Clear where he put forward that a clear idea is defined as one which is so apprehended that it will be recognized wherever it is met with, and so that no other will be mistaken for it. If it fails of this clearness, it is said to be obscure. He argued that to understand an idea clearly we should ask ourselves what difference its application would make to our evaluation of a proposed solution to the problem at hand. Pragmatism (a term he appropriated for use in this context) was asserted by him as a method for ascertaining the meaning of terms (as a theory of meaning). There is much originality in these ideas of his. They rejected a view of knowledge that had been accepted by scientists for some 250 years; that knowledge was an impersonal fact. Peirce contended that we acquire knowledge as participants, not as spectators. He felt that "the real" is that which, sooner or later, information acquired through ideas and knowledge with the application of logical reasoning would finally result in.

G. F. Stout and J. M. Baldwin

G. F. Stout and J. M. Baldwin, in the Dictionary of Philosophy and Psychology , define "idea" as "the reproduction with a more or less adequate image, of an object not actually present to the senses." They point out that an idea and a perception are by various authorities contrasted in various ways. "Difference in degree of intensity", "comparative absence of bodily movement on the part of the subject", "comparative dependence on mental activity", are suggested by psychologists as characteristic of an idea as compared with a perception.

It should be observed that an idea, in the narrower and generally accepted sense of a mental reproduction, is frequently composite. That is, as in the example given above of the idea of chair, a great many objects, differing materially in detail, all call a single idea. When a man, for example, has obtained an idea of chairs in general by comparison with which he can say "This is a chair, that is a stool", he has what is known as an "abstract idea" distinct from the reproduction in his mind of any particular chair (see abstraction). Furthermore a complex idea may not have any corresponding physical object, though its particular constituent elements may severally be the reproductions of actual perceptions. Thus the idea of a centaur is a complex mental picture composed of the ideas of man and horse, that of a mermaid of a woman and a fish.

In anthropology and the social sciences

Diffusion studies explore the spread of ideas from culture to culture. Some anthropological theories hold that all cultures imitate ideas from one or a few original cultures, the Adam of the Bible or several cultural circles that overlap. Evolutionary diffusion theory holds that cultures are influenced by one another, but that similar ideas can be developed in isolation.

In mid-20th century, social scientists began to study how and why ideas spread from one person or culture to another. Everett Rogers pioneered diffusion of innovations studies, using research to prove factors in adoption and profiles of adopters of ideas. In 1976, Richard Dawkins suggested applying biological evolutionary theories to spread of ideas. He coined the term 'meme' to describe an abstract unit of selection, equivalent to the gene in evolutionary biology.

Relationship of ideas to modern legal time- and scope-limited monopolies

Relationship between ideas and patents

On Susceptibility to Exclusive Property

Thomas Jefferson, letter to Isaac McPherson, 13 August 1813

"It has been pretended by some, (and in England especially,) that inventors have a natural and exclusive right to their inventions, and not merely for their own lives, but inheritable to their heirs. But while it is a moot question whether the origin of any kind of property is derived from nature at all, it would be singular to admit a natural and even an hereditary right to inventors. It is agreed by those who have seriously considered the subject, that no individual has, of natural right, a separate property in an acre of land, for instance.

By an universal law, indeed, whatever, whether fixed or movable, belongs to all men equally and in common, is the property for the moment of him who occupies it, but when he relinquishes the occupation, the property goes with it. Stable ownership is the gift of social law, and is given late in the progress of society. It would be curious then, if an idea, the fugitive fermentation of an individual brain, could, of natural right, be claimed in exclusive and stable property.

If nature has made any one thing less susceptible than all others of exclusive property, it is the action of the thinking power called an idea, which an individual may exclusively possess as long as he keeps it to himself; but the moment it is divulged, it forces itself into the possession of every one, and the receiver cannot dispossess himself of it. Its peculiar character, too, is that no one possesses the less, because every other possesses the whole of it. He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me.

That ideas should freely spread from one to another over the globe, for the moral and mutual instruction of man, and improvement of his condition, seems to have been peculiarly and benevolently designed by nature, when she made them, like fire, expansible over all space, without lessening their density in any point, and like the air in which we breathe, move, and have our physical being, incapable of confinement or exclusive appropriation. Inventions then cannot, in nature, be a subject of property.

Society may give an exclusive right to the profits arising from them, as an encouragement to men to pursue ideas which may produce utility, but this may or may not be done, according to the will and convenience of the society, without claim or complaint from anybody. Accordingly, it is a fact, as far as I am informed, that England was, until we copied her, the only country on earth which ever, by a general law, gave a legal right to the exclusive use of an idea. In some other countries it is sometimes done, in a great case, and by a special and personal act, but, generally speaking, other nations have thought that these monopolies produce more embarrassment than advantage to society; and it may be observed that the nations which refuse monopolies of invention, are as fruitful as England in new and useful devices."

To protect the cause of invention and innovation, the legal constructions of Copyrights and Patents was established. Patent law regulates various aspects related to the functional manifestation of inventions based on new ideas or an incremental improvements to existing ones. Thus, patents have a direct relationship to ideas.

Relationship between ideas and copyrights

In some cases, authors can be granted limited legal monopolies on the manner in which certain works are expressed. This is known colloquially as copyright, although the term intellectual property is used mistakenly in place of copyright. Copyright law regulating the aforementioned monopolies generally does not cover the actual ideas. The law does not bestow the legal status of property upon ideas per se. Instead, laws purport to regulate events related to the usage, copying, production, sale and other forms of exploitation of the fundamental expression of a work, that may or may not carry ideas. Copyright law is fundamentally different to patent law in this respect: patents do grant monopolies on ideas (more on this below).

A copyright is meant to regulate some aspects of the usage of expressions of a work, not an idea. Thus, copyrights have a negative relationship to ideas.

Work means a tangible medium of expression. It may be an original or derivative work of art, be it literary, dramatic, musical recitation, artistic, related to sound recording, etc. In (at least) countries adhering to the Berne Convention, copyright automatically starts covering the work upon the original creation and fixation thereof, without any extra steps. While creation usually involves an idea, the idea in itself does not suffice for the purposes of claiming copyright.

Relationship of ideas to confidentiality agreements

Confidentiality and nondisclosure agreements are legal instruments that assist corporations and individuals in keeping ideas from escaping to the general public. Generally, these instruments are covered by contract law.

Are ideas restricted for usage by law?

Depending on the particular subject, they might be. This has evolved to become a confusing and little-understood area of the law, colloquially known as intellectual property. Some legal experts reject the term intellectual property, because (they say) it is purposefully used to oversimplify matters. Detractors posit that the term is intended to divert attention from the original purpose of modern forms of (time- and scope-limited) intellectual property (to promote progress in science and art), into creating the illusion of a moral prerogative that enables ideas to be privately owned. More on this controversy can be found in Intellectual property.

Colloquial uses

The colloquial expression "I have no idea" may be used in any situation where a person is ignorant of something or chooses not to reveal what they know.

See also

• Form
• Meme
• Opinion
• Ideology
• Think tank
• Mental image
• Portal: thinking
• Perception related
• Object of the mind
• Notion (philosophy)
• Thought experiment
• Diffusion of innovations
• Universal (metaphysics)
• Introspection and Extrospection

External links

• Catholic Encyclopedia entry "idea"
• Plato's Middle Period Metaphysics and Epistemology
• Sunil Thacker Procedure for Patenting/Copyrighting an idea

Bibliography

• Paul Natorp, Platons Ideenlehre (Leipzig 1930)
• W.D. Ross, Plato's Theory of Ideas (Oxford 1951)
• M.H. Carre, Realists and Nominalists (Oxford 1946)
• Lawrence Lessig, The Future of Ideas (New York 2001)
• J. W. Yolton, John Locke and the Way of Ideas (Oxford 1956)
• E. Garin, La Theorie de I'idee suivant I'ecole thomiste (Paris 1932)
• Peter Watson, Ideas: a history from fire to Freud, Weidenfeld & Nicolson (London 2005).
• A.G. Balz, Idea and Essence in the Philosophy of Hobbes and Spinoza (New York 1918)
• William Rose Benet, The Reader's Encyclopedia 1965, Library of Congress Card No. 65-12510

Reference

• The Encyclopedia of Philosophy, MacMillian Publishing Company, New York, 1973 ISBN 0028949501 ISBN 978-0028949505

1. Vol 4: 118 - 119
2. Vol 4: 119 - 120
3. Vol 4: 120 - 121
4. Vol 5: 525 - 526
5. Vol 6: 333 - 341
6. Vol 4: 121 - 122
7. Vol 6: 314 - 332
8. Vol 4: 196 - 198
9. Vol 4: 487 - 503
10. Vol 4: 74 - 90
11. Vol 4: 305 - 324
12. Vol 8: 349 -351

• Dictionary of the History of Ideas Charles Scribner's Sons, New York 1973-74, Library of Congress Catalog Card Number 72-7943 SBN 684-16425-6

- Nous

¹ Volume IV 1a, 3a

² Volume IV 4a, 5a

³ Volume IV 32 - 37

- Ideas

Idealogy

Authority

Education

Liberalism

Idea of God

Pragmatism

Chain of Being

• The Story of Thought, DK Publishing, Bryan Magee, London, 1998, ISBN 0-7894-4455-0

aka The Story of Philosophy, Dorling Kindersley Publishing, 2001, ISBN 0-7894-7994-X

Plato, pages 11 - 17, 24 - 31, 42, 50, 59, 77, 142, 144, 150

Descartes, pages 78, 84 - 89, 91, 95, 102, 136 - 137, 190, 191

Locke, pages 59 - 61, 102 - 109, 122 - 124, 142, 185

Hume, pages 61, 103, 112 - 117, 142 - 143, 155, 185

Kant, pages 9, 38, 57, 87, 103, 119, 131 - 137, 149, 182

Pierce, pages 61, How to Make Our Ideas Clear 186 - 187 and 189

Saint Augustine, pages 30, 144; City of God 51, 52, 53 and The Confessions 50, 51, 52

- additional in the Dictionary of the History of Ideas for Saint Augustine and Neo-Platonism

Stoics, pages 22, 40, 44; The governing philosophy of the Roman Empire on pages 46 - 47.

- additional in Dictionary of the History of Ideas for Stoics, also here, and here, and here.

• The Reader's Encyclopedia, 2nd Edition 1965, Thomas Y. Crowell Company, Library of Congress No. 65-12510

page 774 Plato (c.427-348 BC)

page 779 Francesco Petrarca

page 770 Charles Sanders Peirce

page 849 the Renaissance

• This article incorporates text from the old Catholic Encyclopedia of 1917, a publication now in the public domain.
• This article incorporates text from the Schaff-Herzog Encyclopedia of Religion, a publication now in the public domain.
•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)

• Cognition