c Peter King, unpublished
BETWEEN LOGIC AND PSYCHOLOGY:
Jean Buridan on Mental Language*
1. Two Theses About Thought
B
URIDAN
, in common with other philosophers of the four-
teenth century, Jean Buridan holds that thought is literally a
language—a familiar thesis in contemporary philosophy. As
such, thought has a vocabulary, syntax, and formation-rules. Buridan, fol-
lowing Aristotle’s lead in De int. 1 16
a
3–8, recognizes three distinct levels
of language: written, spoken, and mental, associated respectively with the
activities of writing, speaking, and thinking; the languages are hierarchi-
cally ordered, and the ordering is piecemeal rather than holistic: particular
inscriptions are said to ‘immediately’ signify particular utterances, and par-
ticular utterances immediately signify concepts. Hence the vocabulary of
‘Mental Language’ consists in concepts, which are mental particulars—“acts
of the soul” (QM 5.09 fol. 33rb). A concept is a natural likeness of that of
which it is a concept, and it signifies what is conceived by the concept.
Written and spoken terms, which are the vocabulary of languages in their
own right, are said to ‘ultimately’ signify what is conceived by the concept
(SDD 4.3.2 39.13–18). Whereas immediate signification is conventional, the
signification of concepts is natural and the same for all. Thus Mental Lan-
guage is a natural language, unlike spoken or written languages, which are
conventional; it is universal to all thinking beings (other than God), unlike
the diversity of merely conventional ‘natural’ languages such as Danish or
English, and indeed explains the possibility of translation among these lan-
guages. Mental Language therefore functions as the semantics for written
and spoken language. It is the vehicle through which written and spoken
languages are ‘given meaning’ or have an ultimate signification, which, in
the last analysis, is due to the ways in which a concept signifies that of
which it is the concept. The terms of Mental Language are concepts, and
propositions in Mental are acts of thought (QLP 1.7 33.20–28).
*
Presented at the conference “John Buridan and Beyond” held in Copenhagen, Septem-
ber 2001. All translations are mine. See the Bibliography for abbreviations, editions,
and references; when citing Latin texts I use classical orthography and occasionally
alter the given punctuation and capitalization. For details on each of Buridan’s works
see Michael [1985].
– 1 –
2
BETWEEN LOGIC AND PSYCHOLOGY
Concepts are therefore components of two systematic bodies of theory.
On the one hand, concepts are psychological entities. They are literally the
elements of thought: thinking of ϕ just is having a concept of ϕ, which man-
ages to be ‘about’ ϕ in virtue of ‘naturally resembling’ it (QM 6.12 fol. 41vb).
Furthermore, concepts are the primary building-blocks of thought itself. We
acquire them from our interaction with the world, and an adequate psycho-
logical theory should detail the process of concept-acquisition, in light of the
operation of other mental faculties (such as sense-perception). Thus men-
tal language provides a description of the way our minds actually function.
Since the basic conceptual apparatus of all humans is the same, psychology
can be a universal natural science.
On the other hand, concepts also have a semantic dimension. In addition
to descriptive psychology, concepts are normatively governed and have se-
mantic features that can be considered independently of their psychological
properties. Three features characterize Mental Language as a semantic sys-
tem: (i ) universality; (ii ) expressive adequacy; (iii ) unambiguousness. As
for (i ): Since the structure of conceptual thought was held to be the same for
all thinking beings, as described above, the language naturally constructed
from these common constituents is universal.
1
As for (ii ): Since to think of
ϕ just is to have a concept of ϕ, anything that can be thought is express-
ible, and in fact thereby expressed, in Mental Language; hence anything
expressible is expressible in Mental Language. As for (iii ): Since the terms
of Mental Language are concepts having a “natural likeness” to their ob-
jects, an ambiguous term in Mental Language would have to be a concept
applicable to two distinct kinds of things; by definition, it must have a nat-
ural likeness to each group of things, and so is not ambiguous—it is perhaps
a broader concept than we may have originally believed, but not ambigu-
ous.
2
Ambiguity is thus confined to Spoken Language or Written Language,
1
The universality of Mental must be due to its structure, not its content, since two
thinkers may have different (if not disjoint) stocks of concepts, depending on their past
causal interaction with the world. To claim universality for the structure of Mental,
then, is roughly to say that a set of conceptual abilities is common to all thinkers,
in virtue of which each is a thinker. Any thinker can combine simple concepts into
complex concepts, for instance.
2
Buridan avoids amphiboly (and in general ambiguity that arises through combining
terms) by adopting the rule that the subjects of Mental sentences always stand for
what they signify—see SDD 7.3.4: “Sciendum est ergo, ut mihi uidetur, quod supposi-
tio materialis non est nisi ratione uocis significatiuae; nullus enim terminus mentalis in
propositione mentali supponit materialiter, sed semper personaliter, quia non utimur
terminis mentalibus ad placitum, sicut uocibus et scripturis. Numquam enim eadem
oratio mentalis diuersas significationes, uel acceptiones, habet; eaedem enim sunt om-
c Peter King, unpublished