The Sophistical Refutations (Greek: Σοφιστικοὶ Ἔλεγχοι; Latin: De Sophisticis Elenchis) is the final work of the Organon, the traditional collection of Aristotle's logical writings. Like the preceding Topics, its subject matter concerns aspects of logic that are significant for the art of rhetoric, in this case, the identification of fallacies.

The Topics (Greek: Τοπικά; Latin: Topica) is the fifth work in the traditional collection of Aristotle's logical writings, the Organon. Whereas the Posterior Analytics is concerned with scientific demonstration based on true premises, the Topics focuses on dialectic argument based on premises which are merely agreed by common consent to be true. It's subject matter therefore has a large overlap with that of rhetoric.

In the Posterior Analytics, Aristotle moves on from the study of formal rules of reasoning in the Prior Analytics to consider the substantive application of logic to produce scientific knowledge, something which he believes is the product of correct reasoning from true premises. This involves him in addressing Plato's Meno's Paradox, seeking to show how knowledge is possible from a position of former ignorance.

The Posterior Analytics at Amazon.com, .uk, .de, .fr.

Aristotle's Prior Analytics (Greek: Ἀναλυτικὰ Πρότερα; Latin: Analytica Priora) is a central text of the traditional collection of logical works known as the Organon. it introduces the study of syllogisms, investigating how a given pair of premises can lead necessarily to a conclusion which is not contained in either premise.

If all A are B, and all B are C, then all A are C. This is an argument of a syllogism of the first figure, in which the middle term B is the subject of one premise and predicate of the other. In this example the premises are universal afffirmative propositions (all A are B). Aristotle also discusses universal negative propositions (no A are B), particular affirmative propositions (some A are B) and particular negative propositions (some A are not B).

After discussing the kinds of valid argument that can be made with syllogisms of the first figure, Aristotle goes on to consider syllogisms of the second figure, in which the middle term is the predicate of both premises, and of the third figure, in which the middle term is the subject of both premises.

All of this is, perhaps inevitably, rather dry reading. The historian of logic John Corcoran has described the Prior Analytics as 'dense, elliptical, succinct, unpolished, convoluted, and technical, unnecessarily so in the opinion of many.' However, he goes on to note:

It presupposes no previous logic on the part of the reader. There was none available to the audience for which it was written — even for today’s reader a month of beginning logic would be more than enough. However, it does require knowledge of basic plane geometry, including ability and experience in deducing non-evident theorems from intuitively evident premises such as those taken as axioms and postulates a generation or so later by Euclid (fl. 300 BCE). Especially important is familiarity with reductio ad absurdum or indirect deduction. Aristotle repeatedly refers to geometrical proofs, both direct and indirect. It also requires the readers to ask themselves what is demonstrative knowledge, how do humans acquire it, what is a proof, and how is a proof made?

If Corcoran regards the prose of the Prior Analytics as 'perversely reader-unfriendly', he nevertheless makes clear its importance, stating: 'The origin of logic is better marked than that of perhaps any other field of study—Prior Analytics marks the origin of logic. '

Aristotle's On Interpretation (Latin: De Interpretatione, Greek: Περὶ Ἑρμηνείας, Peri Hermeneias) is the second text of the Organon, the collection of short logical works that formed the basis of a traditional philosophical education in much of antiquity and the middle ages.

It begins with an analysis of the basic elements of language, before noting that is only when the parts of speech are brought together to form sentences, that we have propositions that can be said to be true or false. The bulk of the treatise considers the nature of propositions in more detail.

The works most famous passage features the famous sea-battle argument, an early statement of the problem of future contingents.

Free online texts

Biblioteca Online de Ciências da Comunicação: On Interpretation, translated by E.M. Edgehill, PDF file.

The Categories is the first book of Aristotle's Organon, the collection of writings which founded the discipline of logic, and were central to philosophical education for centuries. Setting out to enumerate all the possible kinds of things which can be the subject or predicate of a proposition, Aristotle comes up with the ten concepts that give the book its title: substance, quantity, quality, relation, place, time, attitude, condition, action and affection.

Free online and downloadable texts

Gutenberg: The Categories, translated by E.M. Edgehill. Multiple formats.