Peace and Safety For Your Twentieth of April – A Few Observations on Epicurean Logic by Phillip de Lacy

Peace and Safety to the Epicureans of today, no matter where you might be – Happy Twentieth!

For this month here is an excellent excerpt from an article entitled Contributions of the Herculanean Papyri to Our Knowledge of Epicurean Logic, by Phillip H. de Lacy (Transactions and Proceedings of the American Philological Association, Vol. 68 (1937)).  In this excerpt we see, in the interpretation of an expert in the study of Philodemus, some important points that appear to underlay the Epicurean view of proper logical thinking:


The Epicureans, as Philodemus represents them, made the first thoroughgoing attempt  to  establish an empirical logic – a logic freed from any formal a priori element, by the reduction  of  every proposition to immediate experience.  The empirical logic of the Epicureans was primarily opposed to the Stoics, who placed logic on a completely formal level.  The Stoics directed  in part the course of Epicurean logic, principally by raising objections which the Epicureans endeavored to answer.  In constructing their logic the Epicureans utilized the partial  advances of previous thinkers in the direction of empiricism.  They took from the Empirical Physicians the basic principles of empirical method:  observation, record of past experience, and  inference from similar to similar.  Moreover, they took from Aristotle those elements in his  philosophy which were adaptable to empiricism.  Aristotle had discussed empirical method  primarily as a rhetorical device, rather than a genuine part of philosophy; nevertheless  he  formulated several logical principles that could be used by the Epicureans with little change:


  1. All  knowledge about reality must be derived from perception of objects. This statement  is  in accord with the view that the concrete object is the only primary substance  (Cat. 2 a 11-19).  All knowledge of universals must be derived from the observation of the qualities of particulars.
  2. Truth lies in the correspondence of propositions with concrete  facts.
  3. Propositions about the future are neither true nor false.
  4. Perceptions are always, or nearly always, true.  Falsity lies in judgment.
  5. Thought is psychologically derived from perception through imagination and memory.
  6. Language is conventional in words and structure, but the meanings of words are the same for all men,  because they refer to elements common to the experience of all men.
  7. Generic terms are extensional in reference, for there is no single ontological entity  underlying  them  to which they refer.


Philodemus, in answering the Stoics, maintains that inductive inference is necessarily valid because it is based on a knowledge of the essential nature of things.  In the course of experience notions arise in the mind corresponding to the various kinds of objects that have been experienced. These notions, being taken directly from experience, are reliable indices of  the nature of the objects of experience. They  are used in reasoning as standards of  inconceivability, and as such they establish the essential qualities of things.  The essential qualities of a man, for instance, are those qualities without which a man cannot be conceived to be a man.  The test of inconceivability, therefore, by fixing the definite limits of variation in the nature of objects, provides a ground whereby inductive inferences may be necessarily true.  Having once explained to their own satisfaction the possibility of necessary truths on an empirical level, the Epicureans proceeded to claim that all necessary truths are empirical.  An exclusively formal analysis of propositions, they argued, is impossible, for language is meaningful only when related to the world of sense experience through the medium of the empirically derived.  The whole content and structure of thought are directly referable to sense experience.  Hence all attempts at purely formal analysis, including definition and division,  presuppose an inductive logic.



As Seneca recorded: Sic fac omnia tamquam spectet Epicurus! So do all things as though watching were Epicurus!

And as Philodemus wrote: “I will be faithful to Epicurus, according to whom it has been my choice to live.”

Additional discussion of this post and other Epicurean ideas can be found at the Epicurean Philosophy Facebook Group and

Previous Article
Next Article