graham priest, formalization of dialectic logic
Graham Priest has formalized aspects of dialectical logic (in the Hegelian and Marxist sense) primarily through dialetheism and paraconsistent logic, most recently in a 2023 model of dialectical progression.Tandfonline Priest argues that dialectic involves genuine logical contradictions (of the form $A \land \neg A$) that arise and are then aufgehoben (sublated: both cancelled/overcome and preserved/retained at a higher level). This requires dialetheism—the view that some contradictions are true (or hold)—rather than classical logic, which treats contradictions as explosive (entailing everything via the principle of explosion). He has developed this view over decades, notably in “Dialectic and Dialetheic” (1989/1990 in Science & Society) and related earlier work on change, motion, and tense logic.Journals.sagepub
Core Ideas from Priest’s Account
Dialectical contradictions are logical (not merely pragmatic, rhetorical, or “real” in a non-logical sense). Hegel and Marx’s dialectics assume that certain contradictions hold.
Classical (Frege-Russell) logic is valid in limited domains but inadequate for the full range of dialectical phenomena; a more general (paraconsistent/dialetheic) logic is needed.
Sublation preserves the contradictory elements in a transformed way rather than simply eliminating inconsistency.
Related earlier formal work includes “To Be and Not to Be: Dialectical Tense Logic” (1982), which uses a tense logic based on the Logic of Paradox (LP) to model instants of change where a system can be in both a prior and posterior state (realizing a contradiction), linked to continuity principles and remarks by Hegel and Engels.Link.springer
The 2023 Formal Model (“The Logical Structure of Dialectic”)
In this paper (History and Philosophy of Logic 44(2): 200–208), Priest provides an explicit formal model of dialectical progression using the tools of paraconsistent logic (specifically LP for definiteness; other paraconsistent logics could work).Tandfonline Key elements of the model (informal description from the paper):
A dialectical progression is a sequence of situations/interpretations $S_1, S_2, S_3, \dots$.
In the underlying paraconsistent semantics, a predicate $P$ has an extension $\delta^+(P)$ (things of which $P$ is true) and an anti-extension $\delta^-(P)$ (things of which $P$ is false/$\neg P$ holds). These can overlap, allowing gluts (both true and false).
Progressions occur in triples corresponding roughly to thesis / antithesis / synthesis (or root stage / its negation / negation of the negation):
In the “negation” stage, the situation concerning some object becomes its opposite. In the “negation of the negation,” one returns to something like the root stage but at a “higher” level.
A new concept/predicate typically emerges in the process (required for the Hegelian character of the progression). Technical details (same domain across interpretations, controlled language expansion with new predicates, etc.) appear in an appendix.
The model is applied to concrete examples from Hegel (e.g., the opening dialectic of Being in the Science of Logic) and Marx, showing how they fit the structure.
Priest emphasizes that the model captures the dynamical aspect (how contradictions arise and are sublated) that pure dialetheism alone does not address.
Broader Context
This work sits within a revival of interest in formalizing Hegelian dialectics, reflected in the 2023 special issue of History and Philosophy of Logic (co-introduced by Elena Ficara and Priest) and the related volume The Formalization of Dialectics (edited by Ficara and Priest). Other contributors discuss alternative formal approaches (e.g., conjunctive paraconsistency, hybrid logics, historical attempts by figures such as Günther).Taylorfrancis
Priest’s approach is distinctive in treating the contradictions as dialetheias within a relatively standard paraconsistent framework (LP) and in providing an explicit sequential model of progression and sublation. Critics have debated whether this fully captures Hegel’s developmental notion of truth or the non-formal aspects of dialectic; Priest maintains that dialetheism is required and that the formal tools illuminate the logical structure.
For primary sources, see:
Priest, “Dialectic and Dialetheic” (1989/1990).
Priest, “The Logical Structure of Dialectic” (2023).
Related background in In Contradiction and his work on LP and paraconsistency.
This is a concise overview of the main formal contributions; the papers themselves contain the technical details and textual applications.55 sources
as in an ambiguous figure, which is figure A and not figure B and simultaneously is B&~A
Worked for 4sYes — ambiguous figures provide a natural, everyday illustration of the kind of simultaneous “both/and” structure that dialetheic and dialectical accounts aim to capture.
Take a classic example such as the duck-rabbit (or the Necker cube, Rubin’s vase, etc.). The same lines can be experienced as:
Figure A (duck) and not figure B (rabbit), and, equally and at the same time, as figure B (rabbit) and not figure A (duck).
In logical notation this is roughly:
$$(A \land \neg B) \quad\text{and simultaneously}\quad (B \land \neg A)$$ From these two conjuncts it immediately follows (by ordinary conjunction introduction and simplification) that we have both $A \land \neg A$ and $B \land \neg B$. That is a dialetheia: a true contradiction in Priest’s sense.
How this fits Priest’s framework
In the paraconsistent semantics he uses (LP and its relatives), a situation can assign a predicate both to its extension and to its anti-extension. The ambiguous figure is precisely such a situation: the visual stimulus is both “duck-shaped” and “not duck-shaped” (because it is rabbit-shaped), and vice versa.
The contradiction is not a failure of perception or a mere pragmatic oscillation; under the dialetheic reading it is a genuine feature of the object/situation itself. The figure really is both, and the mind can (and does) register both aspects without the whole description collapsing into triviality. Dialectically, the two aspects stand in a relation of mutual negation that is sublated at a higher level: the single figure that unifies the two contradictory readings. This mirrors the root → negation → negation-of-the-negation progression Priest formalizes.
So your formulation is exact: the ambiguous figure is a concrete case of something that is $A \land \neg B$ and simultaneously $B \land \neg A$, thereby realizing the dialetheic structure that Priest takes to be central to dialectical logic.