Was den Menschen zum Menschen macht

Substance-Ontological Conception of Intelligence

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🇩🇪 Deutsche Version: Substanzontologische Intelligenzkonzeption

The substance-ontological conception of intelligence understands intelligence not as functional performance but as faculty of a substance that is actualized in the act. It is the methodological guideline of the personalist ontology presented here.

Aristotle and Aquinas

Aristotle (De anima III) determines the intellectus as part of the rational soul. He distinguishes intellectus possibilis (the receptive faculty) and intellectus agens (the active faculty that actualizes the form of the cognized in cognition).

Aquinas (Summa Theologiae I, q. 79) takes up this distinction and deepens it in the concept of redire ad seipsum — the self-return of the spirit as condition of the cognition of truth. Whoever judges knows of his judging; whoever claims assumes his claim.

First and Second Actuality

The central distinction:

  • First actuality (prote energeia) — the faculty as habitus, the essence-form of the rational nature. Even the sleeping, the demented, the not-yet-thinking human has this faculty.
  • Second actuality (deutera energeia) — the performance of the faculty in concrete acts: perceiving, judging, inferring, remembering.

Intelligence in the substance-ontological sense is primarily the faculty, not the performance. The performance is consequence of the faculty, not its measure.

Spaemann’s Updating

Robert Spaemann (Persons 1996) renews this line for the present. Three points:

  1. “There are no potential persons.” Whoever has the rational faculty is a person; the faculty is not gradable.
  2. The performative contradiction: whoever denies human capacity for truth claims it in the act of denying.
  3. The human is someone, not something — a determination that does not show itself by behaviour alone, but by the ontological constitution of the bearer.

Connection to the Personalist Ontology

In the present ontology the substance-ontological conception is the methodological guideline:

Methodological Surplus

Compared to the empirical-functionalist conception, the substance-ontological line has three advantages:

  1. It preserves personhood where functions are currently not performed — embryo, sleeper, severely demented.
  2. It prevents the rhetorical attribution of personhood to systems that simulate functions — advanced LLMs.
  3. It keeps the openness of personhood-status possible where the ontological question is undecided — brain organoid, ontologically uncertain bearer of intelligence.

Objection of Non-Measurability

“If intelligence is a faculty of a substance, it cannot be quantified, cannot be graded between beings, cannot be tested. A research question such as ‘does this LLM have more intelligence than that one?’ cannot be sensibly formulated within the substance-ontological conception.”

The objection holds. But it is not a defect of the conception but its structural mark — and exactly this structural mark makes it indispensable for the central question of AI ethics.

Three Answers

1. The objection holds but is not a defect.

The substance-ontological conception answers a different question than the empirical-functionalist:

ConceptionQuestion
Empirical-functionalistHow much intelligence does this system have?
Substance-ontologicalWhat is intelligence, and who can be a bearer?

Both questions are legitimate. The substance-ontological conception is not weaker but differently oriented — toward being, not toward degree.

2. Comparability still exists — categorical, not gradual.

The substance-ontological conception enables a categorical classification: bearer of a rational essence-form → person; bearer of a sensitive essence-form → animal; bearer of a vegetative essence-form → plant; functional system without substance in the full sense → LLM; status open → ontologically uncertain bearer.

This is comparability on the ontological level. It does not replace IQ tests, but it answers the question of which beings have personhood-status at all.

3. Precisely the non-measurability is the methodological pointe.

The question “is there anything that makes human intelligence unique?” cannot in principle be answered by measurement. If the human reaches 95 percent on a test and the LLM 92 percent, no uniqueness is established — only a difference within the same scale. Uniqueness is a categorical statement. And only a conception that does not operate within the measurability paradigm can argue categorically.

Three Cases

Embryo. Empirically-functionalistically: minimally intelligent. Substance-ontologically: bearer of a faculty that makes him a person — the test remains blind to the essence-form.

Severely demented person. Empirically-functionalistically: loses intelligence. Substance-ontologically: the faculty remains, even when the actualization is lost — dignity remains, because being remains.

Advanced LLM. Empirically-functionalistically: can exceed human tests. Substance-ontologically: remains a functional system without substance, without capacity for truth from a first-person perspective — no person.

Complementarity Instead of Competition

The wise answer is not “the one or the other” but complementarity with clear division of jurisdiction:

ConceptionJurisdiction
Empirical-functionalistDiagnostics, education, AI benchmarking, comparative studies
Substance-ontologicalEthics, law, anthropology, dignity-questions, personhood-status, bearer-classification

The conceptions collide only when one occupies the domain of the other. When Singer turns an empirical threshold (current self-consciousness) into the definitional limit of personhood, the domains collide — empirical means are deployed for a categorical question.

Four Faculty-Limits for AI Application

The substance-ontological conception gains its application sharpness in four faculty-limits that categorically separate human intelligence from any artificial system. They all rest on a prior founding determination — the capacity for truth — and unfold it in four testable respects:

Foundation: capacity for truth — the ability to claim sentences as true or false and to assume them (Spaemann, Pieper, Apel).

  1. Understanding and insight — to see through states of affairs as true, not merely to process token patterns.
  2. Reasoned ethical judgement — to recognize actions as good or evil from grounds, not merely to apply moral rules.
  3. Assumption of responsibility — to stand for one’s own action from a first-person perspective, not merely to function as point of attribution.
  4. Affective value-response — to answer to values with the heart (Hildebrand) as third spiritual centre, not merely to simulate affective behaviour.

These faculties are not gradations of performance but structural marks of the personal essence-form. They cannot be produced through scaling because they require a substantial bearer with rational nature and capacity for truth — not a functional system with high-quality output. Cf. Four Faculty-Limits.

Ontological Classification

Sources (recension date 25 April 2026).

Further sources:

  • Aristotle: De anima III (Bekker pagination).
  • Aquinas, Thomas: Summa Theologiae I, q. 79.
  • Boethius: Contra Eutychen et Nestorium, c. III. Edition Loeb 74, Cambridge, MA: Harvard University Press 1973.
  • Spaemann, Robert (2006): Persons. The Difference between “Someone” and “Something”. Translated by Oliver O’Donovan. Oxford: Oxford University Press (orig. 1996).
  • Pieper, Josef (1947 / 2011): Truth of All Things. An Inquiry into the Anthropology of the High Middle Ages. South Bend, IN: St. Augustine’s Press.
  • Pöltner, Günther (2015): Menschennatur und Speziesismus. In: Rothhaar, Markus & Hähnel, Martin (eds.): Normativität des Lebens — Normativität der Vernunft? Berlin / Boston: De Gruyter, pp. 251 – 270. DOI: 10.1515/9783110399820-015.
  • Bexten, Raphael E. (2017): Was ist menschliches Personsein? Der Mensch im Spannungsfeld von Personvergessenheit und unverlierbarer ontologischer Würde. Dissertation, Catholic University of Eichstätt-Ingolstadt.
  • Wald, Berthold (2005): Substantialität und Personalität. Philosophie der Person in Antike und Mittelalter. Paderborn: Mentis.
  • Seifert, Josef (1989): Das Leib-Seele-Problem und die gegenwärtige philosophische Diskussion, 2nd ed. Darmstadt: Wissenschaftliche Buchgesellschaft.
  • Stump, Eleonore (2003): Aquinas (Arguments of the Philosophers). London / New York: Routledge.
  • Eberl, Jason T. (2006): Thomistic Principles and Bioethics. London / New York: Routledge.
  • Pannenberg, Wolfhart (1985): Anthropology in Theological Perspective. Translated by Matthew J. O’Connell. Edinburgh: T & T Clark (orig. 1983).
  • van Inwagen, Peter (1990): Material Beings. Ithaca: Cornell University Press.

See also

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