The founder of the ‘The Lyceum’ and tutor of Alexander the Great.   Aristotle differs with his teacher Plato concerning the reality and comprehensibility of the ‘Ideal’.   Radical idealism, the notion that the universal concepts of things are of greater force than the perception of the particular things themselves, is countered with a tempered view that the particulars are necessary to our knowledge of the ‘Ideal’.  It may even be said that the real ideas arise from the entelechy of things themselves. (see the four causes.)



Aliquis definiverit vinciet – the act of apprehension whereby a term is commonly understood

The first of the 5 Common Topics –   Aliquis definit vincit.

Associated with the first act of reason, or simple apprehension.   A perception proceeds to form a thought, which in turn is abstracted into an idea, and finally denoted by a term.  Terms are the subjects of definition — De-finitio – a ‘bounded’ idea.

  • Who or What is X?
  • What kind of thing is X?
    • Formal or logical cause  (Comprehension, Connotation)
    • Genus and Species
  • What is X not?
  • What are the parts of X?
  • To What group does X belong?
  • What examples of the thing exist?  (Extension, Denotation)
  • Etymological definitions, the history of the word

Grammar includes vocabulary and the practical and theoretical sciences.

Material Logic sets forth the art of definition, division, categories, predication and causes.



What would be considered a fallacy in a dialectical argument becomes a tactic

Fallacies arise whenever an argument, meaning a cogent line of terms, propositions and conclusions, is somehow diverted into an unprofitable stream.   In one point of view, this is unfortunate and profitless.  To the pursuer of the dialectic, for example, the failure to develop the discussion in a revealing way that surfaces truth is a good reason to abandon a discussion.  Those who insist on this sort of distortion are practitioners of contention, believing there is no truth to be found in the first place, or disputation, enjoying the control of a discussion more than its profitable results.  In ancient times, these were designated ‘sophists’.

In another point of view, an argument may be more intended toward persuasion than discovery.   This is the chief characteristic and purpose of rhetoric.  When engaged in rhetoric, the idea of competing goods arises.  In this setting, the rhetor is attempting to move the auditor toward one of several goods.   What would be considered a fallacy in a dialectical argument becomes a tactic, a means to steer the stream of meaning toward a pre-conceived goal.   In rhetoric, it is quite possible to conceal a logical weakness (fallacy of form), an ethical breach (fallacy of distraction), or a lapse of intuition (a material fallacy).  This does not make a purposeful inclusion of this sort of device ethical, but these tactics are effective.

There are so many fallacies, it is tempting to think of Aristotle’s target of ethical behavior: There are infinite paths to failure, but only one to success.  In itself, this idea may be a material fallacy, owing to the meaning of the word success, where there is only one correct choice available to ‘success’.   However, it may be true that all fallacies of argumentation may be of three genera.

Fallacies of Form

  • post hoc ergo propter hoc
  • petitio principii
  • enthymeme (covering a weak premise by mere implication)
  • ad ignorantium  (all propositions must be about something, not nothing)

Fallacies of Distraction – properties include ‘non sequitur’, ‘ignoratio elenchi’

  • ad hominem
  • ad baculum
  • ad verecundiam
  • ad misericordiam
  • ad ignominiam
  • ad populum
  • ipse dixit (fallacy of authority)
  • Fallacies of Procedure (as per Peter Kreeft in Socratic Logic)
    • refuting the argument but not the conclusion
    • refuting the conclusion but not the argument
    • Ignoring the argument
    • Answering another argument (rather than the one given)
    • Shifting the burden of Proof
  • Straw Man
  • Hyperbole

Material Fallacies – properties include, like the fallacies of distraction, ‘non sequitur’ – but in this case due to a failure of intuition, the first act of human reason.

  • amphiboly
  • complex question (could be considered formal fallacy)
  • equivocation
  • emphasis
  • Metaphysical Fallacies
    • Reductionism (typically substituting the material cause for the formal)
    • Fallacy of the Accident (confused with Essence)
    • Confusing quantity with quality
    • Misplaced Concreteness



Material Logic

Material reason provides the content for an argument or proposition, and may produce material fallacies

Sometimes referred to as ‘informal logic’, the content of terms and propositions.

According to the three activities of reason, the process of apprehension especially produces concerns of material logic.

The Ten Categories

  1. Substance
  2. Quantity
  3. Quality
  4. Relation
  5. Place
  6. Time
  7. Posture
  8. Possession
  9. Action
  10. Passion

The Five Predicables

  1. Essence
  2. Accident
  3. Genus
  4. Species
  5. Difference

The Four Causes

  • Efficient
  • Formal
  • Material
  • Final

Material Fallacies may arise by the mis-application of this art.