An atom with a non-neutral charge. It has either more electrons than protons or more protons than electrons. Polyatomic Ions are another form of ion. Both types combine to form Ionic Bonds but only monoatomic ions form Metallic Bonds.

Dialogue by Plato, about a conversation between Socrates and a rhapsode, a professional reciter of poetry, named Ion. It is one of the Socratic Dialogues of Plato, his earlier works, in which Socrates is presented simply challenging the views and opinions of another, and not espousing any particular philosophy of his own (though certain beliefs emerge).

The dialogue begins as Socrates sees Ion coming from Epidaurus, having just competed in a competition of rhapsodes. The conversation soon turns to the question of expertise, or techne; and Ion soon makes the preposterous claim that because he knows the poets, especially Homer, and since the poets write about all subjects, he must naturally be skilled in all things. With its subject set, the remainder of the dialogue is a deconstruction of this statement. Socrates procedes to ask Ion several questions about his art and his beliefs about the origin of his skill. The most famous passage of the dialogue is commonly called the "magnet analogy":

For your skillful recitation of Homer is not an art, as you just claimed, but a divine force which moves you, just as in that type of stone which Euripides called a "Magnet", but most people know as a "Heracleian". And indeed these stones do not only attract rings and pieces of iron, but then convey this same ability to the rings so that they can in turn do the same thing which the stone does, to attract other rings, so that sometimes a great chain entirely of iron and rings is formed from the others. This power is thus conveyed to the others from just that one stone. In just this way does the Muse place her inspiration, and a chain is formed from the inspirations of the other ones who are inspired. For all of the poets of epics take virtue not from their skill but, because they are inspired and possessed, compose all of these great poems, and the lyric poets just the same, just as the Corybantic dancers dance when they are no longer within their right minds, so do the lyric poets, no longer within their right minds, make their beautiful songs...(Ion 533d1-534a2)

This is really the center of the dialogue; the reciter of poetry is at the end of a very long chain, flowing through the poet himself, and beginning with the Muse. Since the poet is "possessed" (taken hold of) by the god while he writes, he can not be the source of the poetry, and so it is unneccessary, and unlikely, that he has any particular or specialized technical knowledge. The passage is one of the crucial points for the argument about the nature of possession and divine inspiration in the ancient world; a man who is "possessed" is "ouk emphrenes", "not in his mind", and suggests a certain internal translation of control has taken place.

The remainder of the dialogue is an application of this fundamental principle; Socrates has already proven that the poet and rhapsode do not possess techne, and it remains only to provide examples. He asks Ion to recite several passages of Homer to demonstrate why, if Homer writes about physicians and chariot-racing, he does not necessarily know anything about medicine or chariots. The dialogue ends, of course, with Socrates' argumentative victory, and Ion's shame-faced retreat.

It would be foolish to read truly modern literary theory into the Ion, but in a sense this is the precursor to the modern removal of the author from the a work's interpretation. Plato, in the voice of Socrates, is arguing that the author is in effect a medium of literature, not its source, and so his personal involvement becomes ultimately irrelevant. It is important also to remember that any reading of Plato is a process in which the reader plays a crucial role; Ion is not, in the same sense that Gorgias or Alcibiades are in the later dialogues, a particularly competent adversary for Socrates. We as readers are naturally expected to challenge the argument and find holes in the philosophy, a continued response to the general philosophical problem which Ion and Socrates have begun.




This writeup is about the meaning of the word ion as it is definied in physics and chemistry. In these sciences, an ion is essentially a charged atom or molecule. This means the particle has either one or more extra electrons, or is missing one or more electrons. If it is missing electrons, it is called a cation, and is positive; if it has extra electrons, it is called an anion and is negative.




One of the most obvious things about an ion is that it is charged. As such, it is affected by electric fields. This means, for instance, you can accelerate it in a particle accelerator. It also means that cations and anions attract each other. As such, it is almost impossible to have a clump of cations in one place and a clump of anions in another, because the electric force is overwhelmingly strong. If you were to take for instance one gram of table salt, split it in sodium cations and chloride anions, and put them on opposite sides of a spoon, the the electric force between them would be around 1020 Newton, which is comparable to the force that keeps the earth in her orbit. As such, separating significant numbers of charges is pretty much impossible, and ionic matter is largely mixed evenly. This is called quasi-neutrality.

Apart from this rather impressive physical property, there is also a chemical change. Because the chemical properties of an atom or molecule are determined by the electrons surrounding the nucleus, having extra or missing electron makes the particle "behave" as a different atom chemically. For instance, a fluorine cation has one extra electron. As such, it has the same number of electrons a neon, a noble gas. This configuration is chemically quite stable. As such, fluorine, and many other substances, are often or almost always found in this ionic form.




Where do we find ions? Well, pretty much all over the place. I'll summarize three places where ions are commonly found


  1. In a salt: A salt is defined as a substance that consists of ions. Table salt is just one example of a salt. Salts are typically formed when a substance that easily loses electrons, such as a metal, meets a substance that easily accepts them, such as a halogen or an organic compound. Because of the strong ionic bonds, salts are quite stable; most have very high melting points.
  2. In a polar solvent: Some salts can dissolve in polar solvents, such as water. These dissolved ions are called electrolytes. In the human body, these electrolytes play a crucial role.
  3. In a plasma: Plasmas are essentially energetic gases, in which some of the molecules are split in ions and free electrons. Most of these ions are cations; anions are more rare, as the plasma is so energetic the free electron state is preferable.
It is interesting to note that both the solution and the plasma are decent to good conductors of electricity. If a salt is melted, it will conduct electricity as well.




This is no more than a short and condensed summary on what an ion is; one could probably spent a lifetime researching ions. The most salient features are that they have an electrical charge, which changes their physical behavior. Furthermore, the extra electrons change the chemical behavior. Ions are essential for biological processes.


A meditation on Plato's Ion

Plato was a Ancient Greek philosopher who lived around 2400 years ago in Athens. Almost all of Plato's surviving writings are dialogues (philosophical plays). Ion is a dialogue between Socrates (Plato's teacher) and Ion, a celebrated performer of poetry.

Although Plato is always interesting, it is often hard to find a positive lesson that can be drawn from his philosophy. Often his philosophical ideas contradict our modern sensibilities too much for us to sympathise with his position. The challenge here has been to read Ion while seeking a positive truth.


Ion begins with its eponymous character declaring that he has recently won a prize for his rhapsody, a result of his being an expert on Homer. Although Ion can’t explain why, this expertise appears to be limited to Homer and none of the other great poets. Another aspect of Ion’s skill which appears inexplicable is that when performing before a crowd, Ion finds himself acutely feeling those emotions expressed by the poem.

Socrates tries to get Ion to explain exactly what it means to be an expert rhapsodist, the difficulty being that Ion is not an expert on many sections of Homer's works, for example those which relate to particular skills, such as medicine. Ion can describe the medical portions of Homer's poems, but because he is not an expert on medicine he cannot explain why Homer's writings on medicine are right.Just before the end of the dialogue Ion claims that his expertise is the same as that of a military general.

Upon hearing this last answer, Socrates claims that either Ion is avoiding answering truthfully, in which case Ion is being dishonest, or else Ion doesn't truly know what the nature of his expertise is, in which case it makes sense (in light of the peculiar facets of Ion's skills mentioned above) that good poetry is the product of divine inspiration. Given the choice between these two characterizations, dishonesty or divinity, Ion chooses the latter.

Art as divine madness:

In Ion Socrates suggests that Muses may divinely inspire the poet, so that the poet experiences their passion for their art as a madness. Socrates offers the analogy of the magnet (the Muse) from which hangs a ring (the inspired poet), and from which ring further rings can be hung (trainers, performers like Ion, and eventually even the audience); the magnetic force which holds up the first ring spread through the entire chain.

Thus there is a vast chain of choral singers and dancers, and their trainers and subtrainers, who are suspended, as if from the magnet, at the side of the rings which hang down from the Muse. (536a)

It is unlikely that the notion of art being the result of the Muses – romantic by today’s standards – was being explicated by Plato with positive intentions. For instance, it is noteworthy that Ion’s dialogue conveys him to the audience as something of a self-important fool, whose ignorance shields him from Socrates’ final insult: forcing him to choose between admitting to dishonesty and external inspiration (and so ignorance).

One analogy for Ion’s understanding of Homer is that he is similar to someone who understands the effects of a drug by seeing what it does to experience; the analogy being that Ion may not be able to justify Homer’s point of view, but is happy to be an expert in seeing the world through Homer . From this is has been argued that Plato’s central argument against poetry is not merely its lack of knowledge (which it professes to possess), but that it is corrupting by teaching us a particular point of view, when in fact what we should be seeking are general truths.

Truths received:

It is initially difficult to take a positive lesson from the main thrust of Ion, which seems to disparage the arts (even if not yet at the stage of The Republic's call for them to be banned). The problem is not only that Plato is showing poetry to be inherently flawed as a medium (which would offend our considerations of art qua cultural expression), but even more basically Plato's showing something to be bad. It is difficult to simultaneously desire to be (actively, and not merely passively) open-minded of a position, and yet have that position be antagonistic to that same open-mindedness.

The question here is not "What is worthwhile in Ion?" but rather "How can Ion (in its summation) be seen as worthwhile?" Thus it is not enough to state that there are valuable lessons to be found interspersed through the text, but rather once the principle thesis of Ion is agreed upon that same thesis needs to be shown as a worthy point of view. This requires some walk-through:

Plato is demonstrating through Ion and Socrates that any truth found in poetry (and its propagators) is accidental, merely stemming from some unrealized external source. This is sufficient insofar as Ion is considered a classic "Socratic dialogue", showing that a certain assumption is weaker than originally supposed (in this case the assumption relates to the expertise of the poet); this is not sufficient insofar as a positive doctrine is being sought. The positive doctrine would be that belief which Socrates holds, and on account of which he is suspect of Ion's knowledge. It would seem that this factor being sought relates in some way to Socrates' criterion for truth and its contrast with Ion's. For Ion a truth can be established by proving its presence – whether simply or hermeneutically – in Homer's texts. Neither a simple nor a hermeneutical linkage to Homer is sufficient for Socrates (since any simple link implies a merely superficial awareness of what the text says about the matter, and interpretations are whimsical exercises ).

The contrast can be illustrated as follows: for Ion it is enough to know what Homer says about driving a chariot, whereas for Socrates it is important to know about driving a chariot irrespective of Homer. Thus although a person may correctly learn truth "A" by means of thing "B", they do not have a proper understanding (per Socrates' criterion for truth) until they are able to separate that which they’ve learnt, "A", from that which they’ve learnt it by, "B".

It follows that a person can conduct the following interview with themselves: "I know this thing 'A'. How do I know it? I know 'A' because I experienced 'B'. What would it mean, or how could I conceptualise 'A' without 'B'?”

Although the exercise seems to reflect some sort of effort at empirical awareness (that is, to be aware of how we know each thing), this is not its purpose. The problem is not only to determine how we know a thing, but rather to make an effort at knowing that thing after cutting it off from its learning process. The aim is not to test that thing, but rather to see it in itself.

This is a lesson we should learn.


  • Pappas, N. Plato's Ion: The Problem of the Author (1951) Philosophy [link]
  • Jowett, B. (translator) Plato's Ion [link] - a minor note on terminology: what Jowett translates as "art" is more akin to what we would call a technique or professional skill, and differs from what I've called "art" in the writeup in which I mean something like an aesthetic product. In Ion Plato seems to hold that the problem with poets is that their knowledge is not a techne, i.e. it is not a technical skill/proper knowledge, although it well should be. Plato is effectively arguing against the post-Romantic tendency to want artists to express their art primitively, without necessarily understanding what they're doing. Thanks to DonJaime for some helpful suggestions.

I"on (I"on), n. [Gr. 'io`n, neut, of 'iw`n, p. pr. of 'ie`nai to go.] (Elec. Chem.)

One of the elements which appear at the respective poles when a body is subjected to electro-chemical decomposition. Cf. Anion, Cation.


© Webster 1913

I"on, n.


One of the electrified particles into which, according to the electrolytic dissociation theory, the molecules of electrolytes are divided by water and other solvents. An ion consists of one or more atoms and carries a unit charge of electricity, 3.4 x 10-10 electrostatic units, or a multiple of this. Those which are positively electrified (hydrogen and the metals) are called cations; negative ions (hydroxyl and acidic atoms or groups) are called anions. Thus, hydrochloric acid (HCl) dissociates, in aqueous solution, into the hydrogen ion, H+, and the chlorine ion, Cl-; ferric nitrate, Fe(NO3)3, yields the ferric ion, Fe+++, and nitrate ions, NO3-, NO3- , NO3-. When a solution containing ions is made part of an electric circuit, the cations move toward the cathode, the anions toward the anode. This movement is called migration, and the velocity of it differs for different kinds of ions. If the electromotive force is sufficient, electrolysis ensues: cations give up their charge at the cathode and separate in metallic form or decompose water, forming hydrogen and alkali; similarly, at the anode the element of the anion separates, or the metal of the anode is dissolved, or decomposition occurs.


One of the small electrified particles into which the molecules of a gas are broken up under the action of the electric current, of ultraviolet and certain other rays, and of high temperatures. To the properties and behavior of ions the phenomena of the electric discharge through rarefied gases and many other important effects are ascribed. At low pressures the negative ions appear to be electrons; the positive ions, atoms minus an electron. At ordinary pressures each ion seems to include also a number of attached molecules. Ions may be formed in a gas in various ways.


© Webster 1913

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