Topic: Socratic Logic (Discussion)

Socratic Logic by Peter Kreeft

Socratic Logic is a logic textbook by American philosopher Peter Kreeft, first published in 2004 and then revised and reprinted in 2010.1) Kreeft perceived a gap in the market, books about logic were either a historical surveys of Socrates, Plato, or Aristotle or primers in symbolic logic.2)

Logic makes your reading and writing clearer, gives you persuasive power, helps you find happiness and gives you the wisdom to find meaning and truth.3)

In 1913 Bertrand Russell and Alfred Whitehead wrote Principia Mathematica which became the foundation for Symbolic logic, which in turn laid the foundations for modern coding (aka programming logic). Kreeft's purpose, however, is to take an Aristotelian approach to logic, systemising a coherent approach to logic in the humanities.4) His starting points are “epistemological realism” which assumes certainty is possible{5) and “metaphysical realism” which assumes that there “universal concepts” that “correspond with reality.”6)

Kreeft provides this overview at the beginning and it forms the foundation for the rest of his work. 7)

Grammatical Structure Mental Action Part of Logic Individual aspects Accuracy
Phrases Concepts Understanding Terms Clear or unclear
Sentences Judgements Judging Premises (Propositions) True or false
Paragraphs Arguments Reasoning Arguments Valid or invalid

Deductive logical arguments should be contain at least two premises and a conclusion.8)

  1. Subject (Term) and verb(Term) = Premise
  2. Subject and verb = Premise
  3. Subject and verb = Conclusion.

Understanding is the first logical act. Terms need to be defined carefully so that they are clear. “A term is the most simple and basic unit of meaning.”9)

Aristotle first formulated the ten traditional categories to describe something.10)

  • Substance
  • Quantity
  • Quality
  • Relation
  • Place
  • Time
  • Posture
  • Possession
  • Action
  • Passion
11) 12) 13) 14)
Minimalist: What distinguishes it? Coextensive: not broad or narrow Clear, Literal, Brief Not negative Or Circular
Maximalist: What makes it distinct?

A nominal (dictionary) definition is part of the search to find an essential definition. Kreeft gives 15 possibilities for “man”, “triangle” and “democracy”.15) The clue to finding the essence of something is to find out if a “thing acts as it is ('operatio sequitur esse').”16)

“To predicate is to affirm or deny a predicate of a subject.”17) Kreeft goes on to write “Symbolic logic has no room for the predicables because the predicables presuppose the forbidden idea of nature, essence, or whatness. The five predicables are a classification of predicates based on the standard of how close the predicate comes to stating the essence of the subject.”18)

Predicate Definition
Species Whole essence
Genus A common aspect
Specific difference Unique only to the essence
Property Flows from, only because of
Accident Sometimes occurs in it

Tree of Porphry, helps you see that the more broadly and simply you define something (extension) the more members your definition will have. In the opposite direction the more specific you are (comprehension), the smaller the group but the more properties you need assign.19)

A form of extension.20)

  1. Exclusive
  2. Exhaustive

style=font-size:100%;line-height:85% |label1=Material Fallacies{{sfn|Kreeft|2010|pp=69-70

                   |1=Eqvuication = ''two different senses''
                   |2=Ambiguity = ''jokes relying on ambigious syntax'' 
                   |4=Straw Man }}
                |label2='''Diversion''' <small>(diverting attention by appeals)</small>
                   |1=Ad hominem =''negative appeal to bad character''
                   |2=Ad verecundiam =''positive appeal to authority''
                   |3=Ad ignominiam = ''appeal to shame'' 
                   |4=Ad populum = ''appeal to the Masses''}}
               |label3='''Oversimplifcation''' <small>(from the part to the whole)</small>
                   |1=Dicto simpliciter = ''stating things too simply''
                   |2=Special Case 
                   |3='Black and White fallacy' = ''not allowing for exceptions''
                   |4=Quoting out of context }}

}} }}

Truth = A direct correspondance with reality.21)

Prepositions = “The subject is what is we talking about. The Predicate is what we say about it.”22)

  • A universal +
  • E universal -
  • I particular +
  • O particular -
Square of Opposition

Calculating the validity of syllogisms.23) “All (s) is (p)”

The square of opposition, finding truth by comparing qualities. 24)

  • Contrary A & E = “a universal + & a universal -”
  • Subcontrary I & O = “a particular - & a particular -”
  • Contradiction A & O, I & E = “a universal + & a particular -” or “a universal - and a particular +”
  • Superalternation A and E, I and O = “a universal + and a particular +” or “a particular + and a particular +”


“We can evaluate arguments as valid or invalid only after we find them.”25) The presence of an argument is shown by the existence of structure (two or more premises and a conclusion) and keywords (therefore, because etc). Create an argument map to chart its strategy.

Diagram of a Syllogism

Three types of arguments:26)

  • Physical relation
  • Logical relation
  • Psychological relation

“And socrates is a man Therefore Socrates is mortal”27)

“The syllogism is the heart of logic. It is the easiest, most natural, and most convincing form of argument. … Consider this classic example:” - Identify the conclusion, and major and minor terms (the noun and verb) and then the major and minor premises.28)

“Science is not identical with induction. … Induction, like deduction, is reasoning, and therefore comes under the third act of the mind, not the first; while abstraction comes under the first act of the mind, not the third, yet there is an analogy between the two.”29) Induction is reasoning from the inside, from particular to the universal.30)


  • Efficient Causes: the agent that makes, moves or changes (origin)
  • Material causes: (contents) “the material cause of the sea is water”
  • Formal causes: the essence (identity)
  • Final causes: the purpose (destiny)

We reason from cause to effect and vice versa. We also need to distinguish between necessary (without it, it cannot happen) and sufficient (must happen). Then we must figure out ultimate and proximate causes or remote and immediate causes.32)

A tool for discovery and thinking.33)

  • Identification of the problem
  • Preliminary hypothesis
  • Relevance
  • Simplicity
  • Testability
  • Compatibility with known data
  • Hypothesis refined
  • Process repeated
  • Power to explain or predict

style=font-size:100%;line-height:85% |label1=Formal Fallacie((Kreeft, //Socratic Logic//, 70)) |1={{clade |label1='''Argumentation''' |1={{clade |1=Non sequitur = ''It does not follow'' |2=Ignoratio Elenchi = ''irrelevant connecting premises and conclusion''

                   |1=Hasty Generalization
                   |2=Post hoc, ergo propter hoc ''after this, therefore caused by this'' }}
                   |1=Refuting an argument by refuting its conclusion = ''need to show full working out''
                   |2=Aussming that refuting the an argument disproves its conclusion = ''a weak argument doesn't disaprove a conclusion''}}
                   |2=Confusing the Accidential with the Essential
                   |3=Confusing Essence with Existence 

}} }} }}

1) 'Socratic Logic', St Augustine Books, http://www.staugustine.net/our-books/books/socratic-logic-3rd-edition/ access-date=30 June 2018
2) Peter Kreeft, Socratic Logic: A Logic Text Using Socratic Method, Platonic Questions and Aristotelian Principles, (South Bend, Indiana: St Augustine's Press, 2010):x
3) Kreeft, Socratic Logic, 1-7
4) Kreeft, Socratic Logic, 15
5) Kreeft, Socratic Logic, 17
6) Kreeft, Socratic Logic, 20
7) Kreeft, Socratic Logic, 27-29
8) Kreeft, Socratic Logic, 30
9) Kreeft, Socratic Logic, 41
10) Kreeft, Socratic Logic, 55
11) Kreeft, Socratic Logic, 123
12) Kreeft, Socratic Logic, 124
13) Kreeft, Socratic Logic, 124
14) Kreeft, Socratic Logic, 124
15) Kreeft, Socratic Logic, 127-129
16) Kreeft, Socratic Logic, 59
17) Kreeft, Socratic Logic, 56
18) Kreeft, Socratic Logic, 57
19) Kreeft, Socratic Logic, 60
20) Kreeft, Socratic Logic, 62
21) Kreeft, Socratic Logic, 145
22) Kreeft, Socratic Logic, 140
23) Kreeft, Socratic Logic, 148-152
24) Kreeft, Socratic Logic, 175
25) Kreeft, Socratic Logic, 190
26) Kreeft, Socratic Logic, 200
27) Kreeft, Socratic Logic, 215
28) Kreeft, Socratic Logic, 215
29) Kreeft, Socratic Logic, 225
30) Kreeft, Socratic Logic, 313
31) Kreeft, Socratic Logic, 202
32) Kreeft, Socratic Logic, 320
33) Kreeft, Socratic Logic, 325-326
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  • Last modified: 2019/06/17 00:11
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