The expression idea (from ancient Greek ἰδέα idéa “shape”, “appearance”, “appearance”, “archetype”) has different meanings in general and in philosophical usage. In general terms, it is understood to be a thought that one can act on, or a guiding principle that one can use as a guide. The philosophical meaning was first shaped in antiquity by Plato and Platonism . In the Platonic doctrine of ideas , ideas are unchangeable, only spiritually comprehensible archetypes, which underlie sensually perceptible phenomena. This understanding of ideas had a strong effect up to modern times, but the term "idea" received different contents in different philosophical directions.
Ancient and Middle Ages
The ancient Greek noun idea originally describes the appearance of something that is seen and makes a certain impression. It is derived as a verbal abstract from idein “behold”, “recognize” ( aorist to horan “see”). While the use of this word began relatively late in literary literature - in Pindar and in the Corpus Theognideum - the older noun eidos to denote visual impressions already occurs frequently in the Iliad . The two words are usually used interchangeably. In general terms, both designate the appearance, shape or shape, an external appearance that is described as beautiful or ugly, for example. It is an appearance that can also be deceptive as mere appearance; the appearance raises expectations that are sometimes disappointed. Not only individual individuals, but also groups and groups have a certain eidos , according to which they can be differentiated: There is a royal and a slave eidos and an eidos of ethnic groups.
The words eidos and idea not only denote an appearance, but in a derived sense also its bearer. What is meant then is a kind or a type of something: a class of people, things or phenomena that is characterized by certain - not just optical - features. For example, in medicine, a certain type of patient is an eidos . If the term is used to designate a type or a kind of something, it can also be a question of non-illustrative facts, for example when talking about different approaches, ways of life, forms of government or types of malice or war. This is about classification based on the nature or a quality that is common to all elements of a group or species and shows itself, for example, in the form of a thing or in the implementation of an action.
Plato coined the concept of philosophical ideas. He did not introduce a rigid terminology, but instead used other expressions, especially eidos , and paraphrases in addition to idea for what were later known as “platonic ideas” . While idea, in the original sense of the word, refers to the visible appearance of something, the Platonic idea, in contrast, is that which is not perceptible to the senses and which underlies the visible appearances. But it can be grasped spiritually and "visible" to Plato in a figurative sense; this explains the transfer of the term idea from the realm of sensory perception to that of a purely spiritual perception. The spiritual "seeing", the "vision" of ideas possible for the philosopher, plays a central role in Platonism.
The materialistic thinker Democritus also used the term idea , albeit in a completely different sense than Plato. He called the atoms of different shapes, of which everything is made according to his teaching, as ideai (forms).
Cicero , who spread Platonic ideas in the Latin-speaking world, contributed to the fact that idea also became a philosophical technical term in Latin literature. He wrote the word in Greek as a foreign word, but later authors usually use the Latin script. In Latin, what Greek thinkers understood by eidos or idea was also used with expressions such as forma ("form"), figura ("shape"), exemplar ("pattern"), exemplum ("pattern", "model") and species ("shape", "pattern", "type"). Seneca spoke of "Platonic ideas" ( ideae Platonicae ). The late antique translator and commentator of Plato's dialogue Timaios , Calcidius , also used expressions such as archetypus , archetypum exemplar or species archetypa (“archetypal pattern”).
The church father Augustine said that although the term “ideas” was first introduced by Plato, the content of this term must have been known long before him. "Idea" is to be translated into Latin with forma or species ; The translation ratio is also acceptable, if not exactly, since ratio actually corresponds to the Greek word logos .
Medieval philosophers and theologians adopted the ancient Latin terminology of the doctrine of ideas, which Augustine, Calcidius and Boethius in particular conveyed to them. In addition to the Latinized Greek word idea, they also used the purely Latin expressions already in use in antiquity to denote the Platonic ideas, especially forma .
In the Christian school philosophy of the early modern period , including among the Jesuits , ideas were primarily understood to be the archetypes in the spirit of God, according to which he had created the world, but also - in analogy to this - designs in the human spirit that enable the realization of Works precede. In a broader sense, ideas in the 17th century were the principles in human consciousness by which it identifies and organizes objects of knowledge, and in general mental contents ( phantasmata ) produced by the imagination , including memory contents . René Descartes defined “idea” in the broadest sense as the content of consciousness of any kind. General usage was based on this broad understanding of the term. The French word idée , derived from idea , was generally used to denote ideas and ideas. In German in the 17th century, the Latin idea was still often used as a foreign word for “concept” and “thought”, but also the French idée , which was then Germanized as “idea” and was ultimately established in this form.
In today's general, non-philosophical usage, "idea" denotes a thought that one can act on, an idea or opinion. Often it is an idea, a new, original, sometimes witty or funny thought that can be put into practice. In this sense, the word can take on the meaning of "plan" and "intention". An idea is also the conceptual draft of an invention, a work of art or a literary creation; In this sense Goethe already spoke of his ideas. Sometimes a principle is meant, a model or a basic idea that determines how a person thinks and acts, for example "the idea of freedom" or "the European idea". In music, the term "idea" occurs for a core theme or leitmotif of a multi-part work.
Colloquially, an idea is also a small amount (for example: add an idea of sugar after stirring the dough ) or something that makes only a slight difference (for example: one idea louder ).
The philosophical conception of ideas goes back to Plato. This is why one speaks of “Platonic ideas” and of Plato's theory of ideas. The introduction of the doctrine of ideas, which did not yet appear in Plato's early works, is often seen as the dividing line between the ideas of the early days, which was influenced by Plato's teacher Socrates, and a completely independent Platonic philosophy. However, Plato does not systematically process his comments on the ideas, he does not present a coherent teaching structure anywhere. Therefore the common term “doctrine of ideas”, which does not come from Plato, is somewhat problematic. In addition, Plato himself points out weaknesses in the conception of ideas.
Plato assumes that the area of the sensually perceptible is subordinate to a real and independently existing realm of ideas that can only be recognized on a spiritual path. Ideas are, for example, “the beautiful in itself”, “the just in itself”, “the circle in itself” or “the human in itself”. The ideas, not the objects of the sensory experience, represent the actual reality. Only they have true being . In contrast to the sense objects, ideas are perfect and immutable; they are not subject to emergence, change and decay. The mode of existence of sensually perceptible objects, on the other hand, is characterized by deficiency. For example, a single thing always has only a limited, relative beauty; it can be surpassed by something more beautiful. In addition, a beautiful sensory object can lose its beauty over time. The idea of the beautiful, on the other hand, is withdrawn from such more or less, because the beautiful as an idea is absolutely beautiful (without gradation or restriction).
Since ideas are real to a greater extent than the individual objects that can be perceived by the senses, they are ontologically (in the doctrine of the hierarchy of things) a higher rank than the sense objects. The ideas are not only superior to the sense objects because of their perfection and are superior in the hierarchy of being, but they are also the cause of their existence. They are the archetypes, the sense objects are their images. Every sense object owes its existence to the objective being of the idea on which it is based, for example a horse to the idea of the horse. It derives its particular characteristics from the various ideas that are involved in its design and give it all of its characteristics (size, color, etc.). Every phenomenon of the physical world has a “share” in those ideas whose influence it is subject to. The respective type of this "participation" ( Methexis ) determines to what extent something has the special quality that it receives from a certain idea: How just a person is results from the way in which he participates in the idea of the just. Thus, the ideas cause the individual sense objects to be as they are. Every idea in which an object participates is present in it.
The thinking of the philosopher should be directed towards the ideas. Because of the generality and immutability of their nature, they are the objects from which real knowledge can be obtained, because all knowledge is based on insight into something universally valid and time-independent, not on observation of the accidental and isolated. The particular, the individual can only be understood and correctly classified in terms of the general. Thus the being-based (ontological) higher ranking of ideas corresponds to a cognitive (epistemic) ranking . Knowledge of ideas can be attained by abstracting from the insignificant peculiarities of the individual phenomenon and directing one's attention to the general which underlies and is common to a number of individual things.
Plato's conception of ideas is thus contrary to the view that the individual things make up the whole of reality and that there is nothing behind the general terms but a human need to construct categories of order to classify the phenomena.
While the Platonists clung to Plato's conception of ideas, it found no approval in the other ancient philosophical schools. Aristotle dealt intensively with her and tried to refute her. In particular, he asserted that the assumption of an ontological gap between the world of ideas and the world of senses is incompatible with the assertion that the world of senses is a product of the world of ideas, because there is nothing that can bridge such a gap and thus enable ideas to influence the world of senses could (“ Chorismos ” argument). In addition, the apparently “general” ideas, if they existed separately, are not general, but only a special kind of separate, individual things. Hence the theory of ideas cannot reduce the particular to the general. Since it offers no explanation for the existence of the sense objects, it does not fulfill the purpose for which it was introduced. The idea of separate ideas next to the sense objects only leads to a hypothetical doubling of the world, which does not contribute anything to the understanding of reality and is therefore unnecessary. In addition, if ideas existed separately like individual things and are therefore individual and not general, they are indefinable because only the general can be defined. Consequently, such ideas are also unrecognizable. Even if ideas and individual things are similar, it does not follow from this that the ideas must be the archetypes of the individual things and that these are copied from them. The idea of participation is not well thought out; it is not a philosophical explanation, just an empty word, a poetic metaphor .
Middle and Neoplatonism
The Middle Platonists combined the conception of ideas with their notions of divine rule in the cosmos. They differentiated between the highest, absolutely transcendent deity, who has no direct relationship to the sensually perceptible world, and the creator god, the demiurge , subordinate to it . The Creator God was considered the active cause of the sense objects, in the ideas one saw the paradigmatic (archetypal) cause, in the matter the material cause . This is known in research as the Middle Platonic "three principles teaching". Most of the Middle Platonists viewed the ideas as thoughts of the transcendent God or the Creator God. They were influenced by the theology of Aristotle, according to which God thinks himself and this is his only activity. But there was also the view that the ideas had an independent existence independent of the divine intellect . The Middle Platonic model was followed by the Jewish thinker Philon of Alexandria , who was strongly influenced by Platonism . He identified the "cosmos of ideas", which is the first image of God, with God's reason, the divine Logos . The logos is the imagined world, according to whose "highly god-like" model God created the visible world. In this way, Philon's ideas take on the role of mediating authority between the transcendent God and the created world.
The Neoplatonists adopted a three-part basic structure of the spiritual world with three hierarchically ordered principles: At the top is the absolutely transcendent “ One ”, below the supra-individual spirit or intellect ( Nous ), followed by the spiritual area. In the nous doctrine, the Neoplatonists started out from considerations of Aristotle, who, however, had not distinguished between the one and the nous. According to the Neoplatonic doctrine, the perfect nous is the world of pure thought. His thinking can only focus on something that is not inferior to him in terms of perfection, for if he thought of something subordinate to him, which is not as perfect as himself, this would impair his perfection. He cannot think one thing, because because of its transcendence it is in principle withdrawn from thinking. Thus he cannot think anything other than himself, that is, what is in him. Hence the objects of pure thought are exclusively the own contents of the nous in their entirety. From this it follows from the Neoplatonic point of view that the nous consists of nothing other than the totality of the Platonic ideas and that it is the only ontological place of the ideas. This position is formulated by Plotinus , the founder of Neoplatonism, in his famous theorem: Ideas exist only within the nous. With this he marks an essential difference between Middle and Neoplatonism. The prevailing view in Middle Platonism was that ideas were something produced by the nous and thus subordinate to it. Therefore, the ideas were located in a separate area outside of the nous. Although there were approaches to a theory of the immanence of ideas in the mind even before Plotinus , he was the first to consistently implement and justify the concept of the identity of ideas with the nous, which was considered an innovation by his contemporaries.
The church father Augustine adopted the main features of the Platonic doctrine of ideas, including the concept of participation. He stated that the ideas were uncreated and immortal. They are the reasons ( rationes ) of things; Everything that arises and passes away is designed according to their pattern and receives from them the totality of its characteristics. Their place is the divine reason ( divina intelligentia ). With this positioning of the ideas, Augustine adopted a Middle Platonic model, which he reinterpreted as Christian by combining it with the doctrine of the Trinity . He identified the divine reason in which the ideas were contained as the Word of God made flesh , Jesus Christ . The word of God is the unshaped form of all shaped things. At the same time it is also a statement of God about himself. In his word - and thus also in ideas - God knows himself. Augustine also understood human knowledge as knowledge of ideas. Knowledge is based on the knowledge of ideas, without it one cannot acquire wisdom. The human knowledge of ideas is possible through participation ( participatio ) in the word of God. The unchangeable truths to which man thereby gains access are inherent in himself and not derived from sensory perception. Sensory perception only points out the knowledge that is already latent in him, so that he becomes aware of it.
Until the middle of the 12th century, the Latin-speaking scholarly world of Western and Central Europe only knew of the works of Plato the dialogue Timaeus , which was only accessible in the incomplete Latin translations by Calcidius and Cicero. The doctrine of ideas was received mainly through late antique writers who conveyed the concept to the Middle Ages in a form influenced by the Middle Ages and Neo-Platonists. In addition to Augustine and Calcidius, who had also written a highly regarded commentary on Timaeus , the Neoplatonic oriented theologian Pseudo-Dionysius Areopagita as well as Boethius , Macrobius and Martianus Capella were very influential conveyors of the Platonic ideas . Above all, the determination of the ideas as timeless archetypes ("forms") that exist in the spirit of God and according to whose patterns he creates the sense objects achieved a lasting effect. The images of the ideas in the created things were called "ideas of origin" ( formae nativae ). A distinction was made between ideas as archetypes and ideas that are common to individual things and are captured using the terms genus and species ( formae communes , ideae communes ).
Aristotle's criticism of the Platonic theory of ideas was known to the scholars of the Chartres school as early as the 12th century . His view was shared by the high and late medieval theologians and philosophers insofar as they did not recognize the ideas as an independent reality, but rather located them in the divine intellect. Thomas Aquinas († 1274) accepted ideas as principles of creation in the spirit of the Creator God, but did not take into account that the ideas in the process of creation were their own causality. He said that they were only form causes , the effective cause is the will of God. Thomas criticized Plato's doctrine of the "separate ideas that are by themselves", referring to Aristotle.
The late medieval sign theoretical nominalism or conceptualism brought an even greater distance from the Platonic theory of ideas . The representatives of this direction fought in the "Universalienstreit" the traditionally prevailing conceptual realism (universal realism, also called "realism" for short). It was about the question of the relation to reality of universals (general terms) and thus about the existence of Platonic ideas. Conceptual realists were the representatives of the traditional Platonic-Augustinian or Aristotelian teachings. They meant that the general terms denote something objectively real. This assumption is the starting point of all medieval ideas based on the traditional Platonic-Augustinian doctrine. It is also the prerequisite for the Aristotelian conception of forms, which, unlike the Platonic ideas, do not exist independently, but are at least actually present in the sense objects as objective givens. According to the nominalists, however, the general terms are only “names” ( nomina ), that is, signs that the human mind needs for its activity. Accordingly, the general has a subjective, purely mental reality in thought and only there. It has no ontological relevance. Wilhelm von Ockham , the spokesman for nominalism based on the theory of signs in the 14th century, denies that ideas have their own reality in the spirit of God. For him the expression “idea” only denotes an object of knowledge insofar as it is known; it only says that something is known, so it does not refer to the object as such, but to the fact of its being known.
Early modern age
René Descartes made a sharp break with the Platonic tradition . He rejected the notion that there is a realm of ideas in the divine spirit that serve as patterns for the created sense objects. Descartes held a thinking of God that precedes creation to be impossible, since God is absolutely simple and his knowledge is identical with his will. Therefore, he did not use the term “ideas” in the Platonic sense, but only to denote the content of human consciousness. In addition to the perceptual content and the fantasy products generated by consciousness, he also included the “innate ideas” ( ideae innatae ) that are potentially present in consciousness and are required for philosophical knowledge. Descartes believed that innate ideas could be transferred from the potency to the act and then made possible a priori knowledge. Thomas Hobbes and John Locke opposed the idea of innate ideas . The sensualistic theory of consciousness founded by Locke , which George Berkeley and David Hume further developed in different ways, denies the existence of consciousness contents which cannot be traced back to perception.
Immanuel Kant counts the ideas in the class of pure concepts and separates them as necessary concepts of reason (“transcendental ideas”) from the mere concepts of the understanding. According to his understanding, an idea can only arise in reason, which according to its nature demands the existence of ideas. Ideas are a priori terms . Their distinguishing feature is that they relate to the unconditioned that is necessarily beyond the realm of all possible experience. Hence, in theoretical terms, as an idea of speculative reason, an idea can never attain a demonstrable objective reality outside of itself; it does not come into consideration as the key to possible experiences; in the area of sensory perception it corresponds to nothing. The ideas do not have an ontological meaning for Kant, but they do have a regulative function for cognition and action. He assigns objective reality to them only in the realm of the practical, explicitly referring to Plato. He describes the moral ideas as archetypes of practical reason, which serve as a guideline for moral behavior. He also accepts “aesthetic ideas” as a special type of idea.
Hegel deals with Plato's theory of ideas and appreciates the pioneering role of the ancient philosopher. In Hegel's philosophical system, especially in his logic, the term idea plays a central role. Here it is given a content that differs from any previous philosophical usage. Hegel defines the idea as the truth of subjectivity and objectivity and as the truth in and for itself, thereby distinguishing himself from the doctrines in which it appears as something subjective, as a mere idea and as unreal. By truth he means the conformity of reality with the concept that creates it. In the idea, Hegel sees the concept that brings the reality that he produces into conformity with itself. He describes it as “the unity of concept and objectivity”. For him, as for Kant, the idea is transcendent as a concept of reason; it is the unconditional, of which “no empirical use appropriate to it can be made”. In contrast to Kant, however, Hegel does not infer from this that the idea is ontologically meaningless. Rather, he attributes the fact that the idea “cannot be given a congruent object in the sense world” to a lack of the sense objects, not the idea. Every single thing arises from the idea, and its reason for existence is to express it as well as possible.
In contrast to the Platonic tradition, Hegel does not ascribe absolute calm to the idea in the sense of immobility, but rather a movement with which it posits a world of finite things that is something different from it, something external to it and in this respect its opposite. In order to be able to set its opposite, it must contain it in itself, it must also show difference and division within itself. Thus it includes what it denies, its own opposite.
The philosophical endeavor aims at the "absolute idea". For Hegel this is “the reasonable concept which in its reality only goes together with itself” and “has its own objectivity as its object in its other”. “Everything else is error, gloom, opinion, striving, arbitrariness and impermanence; the absolute idea alone is being, immortal life, self-knowing truth, and is all truth. It is the only object and content of philosophy. ”The task of philosophy is to recognize the absolute idea in its various forms.
Since the end of the epoch of German Idealism , a number of philosophers - in particular representatives of Neo- Idealism, Neo-Hegelianism , Neo-Kantianism and Neuthomism - have assigned ideas an essential function in the context of their ontological, epistemological or ethical concepts, starting from different definitions of the term idea . Such currents persist to the present day. In the 19th century, however, positivists , left Hegelians and Marxists raised violent objections to the conceptions of metaphysical theories . A resolute opponent of the Platonic doctrine of ideas was also Nietzsche , who also fought against this doctrine as part of his polemics against Platonism. In his Götzen-Twilight he wrote that the history of the doctrine of ideas was the story of an error, the alleged "true world" of ideas had turned out to be a fable; it is "an unnecessary idea, an idea that has become superfluous, consequently a refuted idea".
In the philosophy of the 20th and 21st centuries, the assessment of those thinkers who deny the concept of idea any philosophical relevance dominates. These critics claim that “ideas” cannot explain anything, but only create an illusion of explanation. Even the question of a fixed, context-independent meaning of "idea" is wrong. Ideas are purely subjective constructs about which no verifiable statements can be made. Therefore any preoccupation with them is useless. In this sense, u. a. Wittgenstein and Quine . However, the problems that led to the concept of idea being introduced into philosophical terminology and retained from ancient times to modern times remain unresolved. These include the still open questions of how the general validity of scientific knowledge is to be understood and how the unity of concept and object can be explained.
- Helmut Meinhardt u. a .: idea . In: Historical Dictionary of Philosophy , Volume 4, Schwabe, Basel 1976, Sp. 55-134
- Angelica Nuzzo: Idea . In: Hans Jörg Sandkühler (Ed.): Encyclopedia Philosophy , Volume 2, Felix Meiner, Hamburg 2010, ISBN 978-3-7873-1999-2 , pp. 1046-1057
- Rudolf Eisler : Idea . In: Dictionary of Philosophical Terms (1904)
- George Boas: Idea in the Dictionary of the History of Ideas
- For etymology see Pierre Chantraine : Dictionnaire étymologique de la langue grecque. Histoire des mots , Paris 2009, p. 438; Hjalmar Frisk : Greek etymological dictionary , Volume 1, Heidelberg 1960, p. 708.
- For the deceptive impression see Hans Diller : On the use of εἶδος and ἰδέα in pre-Platonic times . In: Hans-Heinz Eulner u. a. (Ed.): Medical history in our time , Stuttgart 1971, pp. 23–30, here: 24.
- See Hans Diller: On the use of εἶδος and ἰδέα in pre-Platonic times . In: Hans-Heinz Eulner u. a. (Ed.): Medical history in our time , Stuttgart 1971, pp. 23-30. Wilhelm Pape : Greek-German Concise Dictionary , 3rd Edition, Volume 1, Reprint Graz 1954, p. 1235, and Henry George Liddell , Robert Scott : A Greek-English Lexicon , 9th Edition, Oxford 1996, provide numerous examples of the ancient use of idea , P. 817.
- On Plato's use of the term see Michael Erler : Platon (= Hellmut Flashar (Hrsg.): Grundriss der Geschichte der Philosophie . Die Philosophie der Antike , Volume 2/2), Basel 2007, p. 391f .; Christian Schäfer : Idea / Form / Shape / Essence . In: Christian Schäfer (Ed.): Platon-Lexikon , Darmstadt 2007, pp. 157–165, here: 157.
- Democritus, fragment DK 68 A 57.
- Evidence in the Thesaurus linguae Latinae , Volume 7/1, Leipzig 1964, Col. 178f.
- Seneca, Epistulae morales 58, 26.
- For the terminology of Calcidius see Gangolf Schrimpf u. a .: idea. II. Middle Ages . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 65-102, here: 65f.
- Augustine, De diversis quaestionibus 46.
- Gangolf Schrimpf et al. Offer numerous examples of the medieval history of concepts. a .: idea. II. Middle Ages . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 65-102.
- On the use of the term in the 17th century see Wilhelm Halbfass: Idea. III. In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 102–113, here: 102–105.
- Hans Schulz: German Foreign Dictionary , Volume 1, Strasbourg 1913, pp. 279f .; Jacob Grimm , Wilhelm Grimm : German Dictionary , Vol. 4/2, Leipzig 1877, Sp. 2039–2041, here: 2040.
- Examples of the modern use of terms are provided by Ruth Klappenbach, Wolfgang Steinitz : Dictionary of German Contemporary Language, Vol. 3, Berlin 1969, pp. 1928f. and the Duden dictionary: Duden. The large dictionary of the German language in ten volumes , 3rd edition, Vol. 4, Mannheim 1999, pp. 1903f.
- See the research overview by Michael Erler: Platon (= Hellmut Flashar (Hrsg.): Grundriss der Geschichte der Philosophie. Die Philosophie der Antike , Volume 2/2), Basel 2007, pp. 390–395 and Dorothea Frede : Platon: Philebos. Translation and Commentary , Göttingen 1997, pp. 333-340; Christian Schäfer: Idea / Form / Shape / Essence . In: Christian Schäfer (Ed.): Platon-Lexikon , Darmstadt 2007, pp. 157–165, here: 158; Thomas Alexander Szlezák : The idea of the good in Plato's Politeia , Sankt Augustin 2003, pp. 54–57.
- Michael Erler provides a comprehensive introduction: Platon , Munich 2006, pp. 142–146. The presentation of the theory of ideas in Giovanni Reale is more detailed: To a new interpretation of Plato , Paderborn 1993, pp. 135–198.
- See also Volker Langholf: Medical Theories in Hippocrates , Berlin 1990, pp. 195-204 (examples from medicine).
- Johannes Hübner: Aristotle on Separation and Causality , Hamburg 2000, pp. 92–94.
- Chung-Hwan Chen: The Chorismos Problem in Aristoteles , Berlin 1940, p. 93f.
- Chung-Hwan Chen: The Chorismos problem in Aristoteles , Berlin 1940, p. 104f.
- Aristotle, Metaphysics 987b7-14, 991a20-22, 1079b24-26. Cf. Francesco Fronterotta: ΜΕΘΕΧΙΣ , Pisa 2001, pp. 397-412; Rolf Schönberger : Participation . In: Historical Dictionary of Philosophy , Volume 10, Basel 1998, Sp. 961–969, here: 961.
- Sources on this in Heinrich Dörrie , Matthias Baltes : Der Platonismus in der Antike , Vol. 4, Stuttgart-Bad Cannstatt 1996, pp. 118–123 (Commentary, pp. 387–399).
- Wolfgang L. Gombocz: The philosophy of the outgoing antiquity and the early Middle Ages , Munich 1997, p. 21f .; Roger Miller Jones: The Ideas as the Thoughts of God . In: Clemens Zintzen (Ed.): Der Mittelplatonismus , Darmstadt 1981, pp. 187–199; Audrey NM Rich: The Platonic Ideas as the Thoughts of God . In: Clemens Zintzen (Ed.): Der Mittelplatonismus , Darmstadt 1981, pp. 200–211 (in places incorrect translation of Rich's essay The Platonic Ideas as the Thoughts of God . In: Mnemosyne Series 4 Vol. 7, 1954, p. 123 -133).
- Helmut Meinhardt: Idea. I. Antiquity . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 55–65, here: 61f.
- Jens Halfwassen : Plotin and the Neo-Platonism , Munich 2004, pp. 64f., 74–77.
- Augustine, De diversis quaestionibus 46.
- Helmut Meinhardt: Idea. I. Antiquity . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 55–65, here: 63f.
- Augustine, De diversis quaestionibus 46.
- Helmut Meinhardt: Idea. I. Antiquity . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 55–65, here: 64.
- Latin ideae separatae , also formae separatae or species separatae per se subsistentes .
- Thomas Aquinas, Summa theologiae I quaestio 6 articulus 4.
- Ockham's position is described by Jan Peter Beckmann : Wilhelm von Ockham , Munich 1995, pp. 98-134. Beckmann offers a brief summary in the Idea article . II. Middle Ages . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 65-102, here: 99-101.
- overview is provided by Angelica Nuzzo: Idea . In: Hans Jörg Sandkühler (Ed.): Enzyklopädie Philosophie , Volume 2, Hamburg 2010, pp. 1046-1057, here: 1053f. and Karl Neumann: Idea. IV. 1st Kant . In: Historical Dictionary of Philosophy , Volume 4, Basel 1976, Sp. 113–119.
- On Hegel's reception of Plato see Werner Beierwaltes : Distance and Proximity of History: Hegel and Plato . In: Werner Beierwaltes: footnotes to Plato , Frankfurt am Main 2011, pp. 303-324.
- On Hegel's determination of the status of the idea, see Charles Taylor : Hegel , Frankfurt am Main 1978, pp. 428–456 as well as the summarizing descriptions by Lu De Vos: Idea . In: Paul Cobben u. a .: Hegel-Lexikon , Darmstadt 2006, pp. 264–269 and Klaus-Dieter Eichler : Idea . In: Petra Kolmer, Armin G. Wildfeuer (ed.): New Handbook of Philosophical Basic Concepts, Volume 2, Freiburg 2011, pp. 1186–1199, here: 1195–1197.
- Hegel: Science of Logic II (= Hegel: Werke , Vol. 6, edited by Eva Moldenhauer and Karl Markus Michel ), Frankfurt am Main 1986, p. 464.
- Hegel: Science of Logic II (= Hegel: Werke , Vol. 6, edited by Eva Moldenhauer and Karl Markus Michel), Frankfurt am Main 1986, p. 462.
- Hegel: Science of Logic II (= Hegel: Works , Vol. 6, edited by Eva Moldenhauer and Karl Markus Michel), Frankfurt am Main 1986, p. 463.
- Charles Taylor: Hegel , Frankfurt am Main 1978, p. 428.
- Charles Taylor: Hegel , Frankfurt am Main 1978, p. 428.
- Hegel: Science of Logic II (= Hegel: Works , Vol. 6, edited by Eva Moldenhauer and Karl Markus Michel), Frankfurt am Main 1986, p. 549.
- Friedrich Nietzsche: Götzen-Twilight . In: Friedrich Nietzsche: Works in three volumes , ed. by Karl Schlechta , Vol. 2, Munich 1966, pp. 939-1033, here: 963.
- Klaus-Dieter Eichler: Idea . In: Petra Kolmer, Armin G. Wildfeuer (eds.): New Handbook of Philosophical Basic Concepts, Volume 2, Freiburg 2011, pp. 1186–1199, here: 1186f., 1189.