[2.7.3] Boethius on Universals

Boethius (477-525 AD), in his second commentary on Porphyry’s Isagoge (see [2.5]) presented a theory of universals characterized by moderate realism, responding to Porphyry’s questions:

Porphyry’s questionsUniversals according to Boethius
(a) whether genera and species are real or are situated in bare thoughts aloneare in the mind
(b) whether as real they are bodies or incorporealsare incorporeals
(c) whether they are separated or in sensibles and have their reality in connection with themare in connection with the sensibles

Boethius model of universals is in the following OntoUML diagram:

Boethius on universals
MindThe “separation in thought of those things that cannot be separated in reality is the process of abstraction. In general, by means of the process of abstraction, our mind (in particular, the faculty of our mind Aristotle calls active intellect (nous poietikos, in Greek, intellectus agens, in Latin) is able to form universal representations of particular objects by disregarding what distinguishes them, and conceiving of them only in terms of those of their features in respect of which they do not differ from one another.” (Klima 2017)
Universalsuniversals are regarded as universal mental representations existing in the mind […]. On this Aristotelian conception, universals need not be thought of as somehow sharing their being with all their distinct particulars, for their being simply consists in their being thought of, or rather, the particulars’ being thought of in a universal manner. This is what Boethius expresses by saying in his final replies to Porphyry’s questions the following:
‘… genera and species subsist in one way, but are understood in an another. They are incorporeal, but subsist in sensibles [individuals], joined to sensibles [individuals]. They are understood, however, as subsisting by themselves, and as not having their being in others.” (Klima 2017)
Genus“The genus is the part of the real definition that answers the broad question What is it? What is man? Man is an animal.” (see also [2.5])(Spade 2009)in the (part of the) Mind; is in a recursive association with itself; each level splits the superior level in 2 or more, based on the attributes marked in Difference
Species“Man is a most specific species. Below man there are only individual men, not yet lower species. What this means, of course, is that the differences among individual men are not essential differences but accidental ones. If they were essential differences, then we would have lower species after all.” (see also [2.5]) (Spade 2009)subkind of Genus; subsists in, joined to Individual
Individual“Below man [as species] there are only individual men, not yet lower species. What this means, of course, is that the differences among individual men are not essential differences but accidental ones.” (see also [2.5]) (Spade 2009)

Related posts in theory of Universals: [1.2.2], [1.3.1], [1.3.2], [2.5], [2.7.3], [4.3.1], [4.3.2]


  • Klima, Gyula, “The Medieval Problem of Universals”The Stanford Encyclopedia of Philosophy (Winter 2017 Edition), Edward N. Zalta (ed.)
  • Spade, Paul Vincent, “History of the Problem of Universals in the Middle Ages”, Indiana University 2009

First published: 04/06/2020

[2.7.2] Boethius on Topical Logic

The area of topical logic, – like many others – was founded by Aristotle in his work “Topics”, and continued by Cicero and Boethius, whose work exercised an enormous influence on medieval logic.
The aim of topical logic is to provide a practical heuristic method for finding credible, plausible (not necessarily true) arguments which can be used in situations where persuasion is needed, e.g. in a legal process. Boethius, in his book “On Topical Differentiae” presents topical arguments in a quasi-syllogistic structure, thus finding a good argument is identifying the middle term which links the extremes (see [1.3.9]).

The following OntoUML diagram presents the main concepts in the Topical Logic of Boethius (477-525 AD):

Boethius on topical logic
ClassDescription Relations
TopicTopic (locus) can be Differentiae and Maximal Sentences.
DifferentiaeTopical Differentiae are the common, caracteristic, distinctive feature, which classifies the Arguments, and the MaximalSentences also.
Boethius lists over 30 Differentiae, like:
“from the lesser”
“from an efficient cause”

A Differentiae is assotiated with at least one MaximalSentence; and with 0, 1 or many Arguments
MaximalSenteceMaximal Sentence (maxima propositio) is a Topic which is somehow shown to be universal or readily plausible. This way “will help to suggest exactly what sort of argument can be made using the differentia in question”, gives power to the Argument.
E.g. for the Differentiae “from an efficient cause” he lifts the following Maximal Sentences:
“Those tings who have a natural efficient cause are themselves also natural.”
– “Where there is the cause, the effect cannot be ansent.”
– “Everything should be considered according to its causes.”
ArgumentArguments are credible, acceptable inferences, whose premises can be valid, or commonly accepted, (not necessarily valid) assertions (see [1.3.9]). Each Argument contains a MiddleTerm
MiddleTermSee in [1.3.9] also: The term shared by the premises is the Middle Term. MiddleTerm is are a role of a Term
TermSee in [1.3.9] also: Subjects and predicates of Arguments are Terms which can be either individual, e.g. Socrates, or universal, e.g. human. Subjects may be individual or universal, but predicates can only be universals.

The UML activity diagram below shows the heuristic process of topical logic:

Boethius: heuristics of topical logic


  • All citations from: Marenbon, John, Boethius, Oxford University Press, 2003
  • Case presented in Activity Diagram from: Marenbon, John, “Anicius Manlius Severinus Boethius”The Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta

First published: 27/06/2019