Posterior AnalyticsEdit
Posterior Analytics is Aristotle’s methodical survey of how human knowledge becomes certain through demonstration. Written as part of the broader Organon, it picks up where the Prior Analytics leaves off, asking not merely what counts as a true proposition, but how propositions acquire necessity when they are supported by premises that are themselves known with greater certainty. At its core, Posterior Analytics argues that scientific knowledge (episteme) rests on demonstrations—deductive inferences that connect universal, indivisible premises to conclusions through the middle term. The work is therefore less a collection of abstract claims than a program for building a stable, rational account of how we come to know the world.
Aristotle’s project presumes that human inquiry seeks explanations in the form of causes and principles that render the world intelligible. To achieve this, the analyst must move from universally accepted premises to particulars by way of demonstration. The book is a prime source for the distinction between opinion (doxa) and knowledge (episteme), between what is merely true for many and what can be established as a universal truth through reasoning. Its lexicon—terms, definitions, predicables, and the structure of the syllogism—has shaped Western logic and the discipline of science for centuries. For readers who explore Aristotle’s broader theory of knowledge, Posterior Analytics connects with Aristotle’s other works on Definition, Genus and Species, and the logic of Syllogism within the Organon.
Overview
- What counts as knowledge: Aristotle insists that scientific knowledge must be about causes and reasons, and must be demonstrable from premises that are already known. This puts the bar high: conclusions must follow with necessity, not merely probability. The movement from self-evident or first principles to demonstrable conclusions is the backbone of the proper science.
- The role of universals: Demonstrations operate with universal propositions (for all x, if x has property P then property Q), because universals provide the stable framework from which particular instances can be derived. Premises must express universals or be reducible to universals through definition and division.
- The structure of demonstration: A demonstration is a chain of syllogisms in which the middle term unites the premises with the conclusion. The middle term must be present and essential to the reasoning, and the connection from premises to conclusion must be necessary rather than contingent.
- First principles and explanation: The premises of a demonstration cannot be merely assumptions; they must be known with greater certainty, often as first principles or self-evident truths. These first principles serve as the anchors of scientific knowledge.
These themes appear across sections that discuss the nature of the syllogistic, the proper arrangement of premises, and the criteria by which a proposition can be considered scientifically proven. The discussion is deeply formal, but Aristotle ties the formal structure to a broader epistemic aim: to secure reliable, intelligible knowledge about the world by grounding conclusions in firm, demonstrable grounds. For readers tracing the lineage of argumentation, see Demonstration and Episteme as central concepts, while the mechanics of argument are clarified through discussions of Syllogism and the Middle term.
The theory of demonstration
A demonstration, in Aristotle’s terms, is an argument where a conclusion follows of necessity from premises that are already known to be true. The prerequisites are strict: the premises must be true, primary (not derived from prior demonstrations of the same kind), and more knowable than the conclusion. This last criterion helps prevent circularity and ensures that the demonstration advances knowledge rather than merely restating it. The middle term—what binds the premises to the conclusion—must be a genuine link, not a mere lexical bridge.
The arrangement of syllogistic form plays a critical role. Aristotle’s analysis of syllogisms—logical arguments built from three terms arranged in subject and predicate relationships—provides a blueprint for ensuring deductive certainty. The process relies on the universality of terms: by moving from universal premises about kinds and their essential properties to conclusions about particular instances, the mind confirms general truths that would hold in all similar cases. See Syllogism and Middle term for more on the logical architecture.
Posterior Analytics also addresses the methods by which we justify our premises. Some premises are known by nature, some through demonstration, and others through experience whether ordinary or experimental. The aim is to show that even what we consider certain knowledge rests on a chain of justified steps, each supported by a prior commitment to universal principles. The relationship between demonstration and experience is thus not a simple either/or; rather, experience can supply the material content, while demonstration supplies the form that makes knowledge secure. For contrasts and connections, explore Induction and Deduction as complementary methods in Aristotelian epistemology.
First principles, definitions, and universals
A distinctive feature of Posterior Analytics is its insistence that first principles must be known and accessible to the mind before they can function as premises in demonstrations. These first principles are not arbitrary; they are the most secure general truths we can grasp about a subject. Definitions play a crucial role in shaping the content and scope of a demonstration by fixing the genus and the specific difference that characterize a term or a proposition. Through definition, the analyst places a concept in a intelligible framework, enabling universal propositions to be formulated and used as premises in demonstration. See First principles and Definition for more detail, as well as Genus and Species for how Aristotelian taxonomy structures knowledge.
The insistence on universals reflects Aristotle’s broader view that science aims at universals rather than merely at the contingent, singular cases. Without universal premises, a chain of reasoning would fail to secure necessity. This emphasis contributes to the long-standing claim that Aristotelian science seeks stable, explanatory accounts of why things are as they are, rather than merely cataloging what happens. For a broader discussion of universals in Aristotelian reasoning, consult Universal (philosophy) and Predicables.
Method and epistemology: science, reasoning, and the scope of knowledge
Posterior Analytics sits at an intersection of rationalist and empirical strands in ancient thought. On the one hand, it defends a rigorous, deductive method: if your premises are solid, the conclusions must follow with necessity. On the other hand, Aristotle accepts that human knowledge begins with experience and observation, since we must learn universal principles from the world before we can demonstrate them. This synthesis offers a model for a science that is both principled and grounded in real-world inquiry. For a broader frame, see Science and Empiricism as historical terms, and note how Aristotle’s approach contrasts with later strict empiricism or purely formal deduction.
The work also engages with the limits of demonstration. Not all knowledge starts from premises that are themselves demonstrable; in some cases, the premises are taken from prior accepted authorities or from those endoxa (widely held beliefs) that are held to be true by reasoned agreement. This makes Posterior Analytics a practical guide to the boundaries of what we can claim as certain knowledge, and to how one might advance from accepted starting points toward more secure conclusions. For further reading on the dynamics between accepted premises and new conclusions, see Endoxa (the Aristotelian concept of credible opinions) and Epistemology.
Reception, influence, and debates
The influence of Posterior Analytics extends through late antiquity into medieval thought and beyond. In the medieval universities, the formal apparatus of demonstration and syllogistic shaped the way scholars approached theology, natural philosophy, and formal logic. The work helped ground the scholastic project of reconciling faith with reason by insisting on demonstrable knowledge where possible and by clarifying what counts as a solid premise. The medieval synthesis is visible in the works of Thomas Aquinas and other scholastic writers, who integrated Aristotelian demonstration into a broader religious and metaphysical framework. See Scholasticism and Aristotelianism for further context.
In modern interpretation, some readers critique Aristotle for overemphasizing universal deduction at the expense of recognizing diverse kinds of reasoning and the contingency of particular cases. Critics outside the Aristotelian tradition might argue that strict demonstration can overlook historical complexity or the role of interpretation in scientific practice. Proponents, however, would contend that the discipline and clarity of demonstration—when properly grounded in firm premises—provide a durable standard for knowledge that supports orderly inquiry, reliable governance, and consistent reasoning in public life. For related discussions, consult Rationalism and Deduction.
Controversies over the proper role of universals, essentialism, and the nature of scientific knowledge continue to echo in contemporary debates about method and evidence. From a tradition that prizes orderly reasoning and universal principles, the criticisms of those who stress social construction, relativism, or the primacy of experience are often viewed as neglecting the value of stable, objective grounds for understanding. In such a view, woke critiques that aim to rewrite the basis of knowledge or to de-emphasize universal reasoning are seen as jeopardizing what has allowed civil society to rely on predictable rules and tested methods. See Nominalism, Essentialism, and Philosophy of science for broader debates.
Texts, translations, and later developments
Aristotle’s original Greek text of Posterior Analytics has been transmitted through the centuries with varying interpretive emphases. The work is frequently studied alongside the other Analytics in the Organon, especially the Prior Analytics, to understand the full arc of Aristotle’s logic and epistemology. Modern readers often encounter discussions of the Syllogism in conjunction with discussions of Induction and Deduction as characteristics of Aristotelian method. For accessible overviews and translations, see Aristotle and the related discussions of Logic and Epistemology.
In later philosophical history, the revival of interest in Aristotelian logic during the Middle Ages and in early modern scholarship kept Posterior Analytics at the core of arguments about what can be known and how we justify our beliefs. The treatise influenced the development of formal logic, and its insistence on the necessity of demonstration continues to inform how philosophers and scientists articulate the foundations of their theories. See Medieval philosophy and History of logic for extended context.