Posterior Analytics (Analytica Posteriora)

Aristotle claims that scientific knowledge is knowledge of why something is so, achieved by demonstrating a conclusion from premises that state its cause. He rejects two ways of avoiding the regress of proof: that demonstration can go on infinitely, and that premises can justify one another in a circle. Both would make knowledge impossible, he argues, so demonstrations must begin from principles that are not themselves demonstrated. This yields a foundational model of science in which explanation, not mere derivation, is what makes an argument demonstrative.

The closing chapter of the treatise addresses this directly. Aristotle argues that principles cannot be innate in a fully formed state, nor derived by demonstration, since demonstration presupposes them. Instead, perception gives rise to memory, repeated memories to experience, and experience to a grasp of the universal. The faculty that apprehends the principles is nous, intellectual insight. The passage is brief and compressed, and interpreters disagree about whether it describes a literal induction, a kind of intuition, or a gradual conceptual formation.

The Prior Analytics develops the theory of the syllogism, the formal machinery of valid deduction. The Posterior Analytics asks what additional conditions a syllogism must meet to count as scientific demonstration: its premises must be necessary, explanatory, and more fundamental than the conclusion. The two works are therefore traditionally paired, and together with the Categories, On Interpretation, Topics, and Sophistical Refutations they form the collection later called the Organon. Reading the Posterior Analytics without the syllogistic theory behind it makes much of its technical vocabulary opaque.

This is a long-standing scholarly question. Jonathan Barnes, in his commentary, argued that the treatise describes an ideal of finished, axiomatized science and not the practice Aristotle follows in his biological or physical works, which proceed through inquiry and dialectic. Others stress that the work is about the structure of settled understanding, which can be reached only after investigation. The mismatch between the demonstrative ideal and the exploratory character of the Physics or the History of Animals is one reason scholars debate whether the treatise is a methodology or a theory of explanation.

A common oversimplification treats it as a rigid recipe for deductive science, or as a crude forerunner of empiricism. In fact it is concerned with the structure of knowledge once achieved, in particular with how explanation and necessity fit together, and it gives induction only a brief, foundational role. Another misreading assumes that it applies equally well to ethics. Aristotle elsewhere, in the Nicomachean Ethics, cautions that ethical subject matter admits less precision, so the demonstrative ideal should not be imposed directly on practical reasoning.

The work survives in Greek and is difficult, so commentary matters as much as translation. Jonathan Barnes's translation and notes in the Clarendon Aristotle series is a standard scholarly choice, and the revised Oxford Translation of Aristotle's complete works, edited by Barnes, is widely used. W. D. Ross's Greek edition with commentary remains a reference for the text. Readers should compare how translators render key terms such as epistēmē, nous, and aitia, since choices such as 'understanding' versus 'scientific knowledge' shape interpretation.