Among the more popular scholastic axioms is the following:

What is supreme in a genus is cause of everything in the genus.

But what is the justification for this principle? Aquinas tends to justify it using examples of heat and light:

That thing will be the cause of all in a certain genus, to which thing the predication of that genus belongs above all: hence that which is most hot is seen to be the cause of heat in all things hot, and that which is most light is the cause of all things that have light (Summa Contra Gentiles II.15.3).

It would be hard to get modern science to agree with his treatment here of heat and light. So is there any way to salvage the principle? Or is the principle simply false, or meaningless?

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    Outside biology, modern science does not use the genus-differentia concept. Commented May 30 at 9:16
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    This replicates a passage from the fourth way in Summa Theologiae discussed by Augros. In Response 8, he admits that the fire example is erroneous and quotes Aquinas himself qualifying this 'principle' in Quaestiones Quodlibetales:"It happens that what is prior among the species of the same genus is a principle and cause of the others... but nevertheless this is not universally true. For man, who is the most perfect species of animal, is not the active cause of the other species."
    – Conifold
    Commented May 30 at 9:37
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    Augros then quotes the source of this 'principle' in Aristotle ("if something belongs to two things, but to one of them because of the other, then it belongs more to the cause", Metaphysics II.1 993 b23) and derives from it two stipulations for Aquinas's formulation to hold:"When must this be true? Whenever two conditions are met: 1. When the things in the genus need a cause, and 2. When it is not possible for the cause of the things in the genus to be outside that genus. When these two conditions are met, it must be true that the maximum in the genus is the cause of all in the genus."
    – Conifold
    Commented May 30 at 9:40
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    I recognized the argumentation from the fourth way and then searched for a commentary on it with "what moreover is the greatest in its genus, in another way is the cause of all things of its genus" added for more specificity.
    – Conifold
    Commented May 30 at 10:02
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    Keep in mind that Aristotelian causes are not really comparable to causes in modern science. I'm not sure that statement can even be translated into modern scientific language. Commented May 30 at 11:52

1 Answer 1


This is the Aristotelian principle of teleology, the manifestation of which is enclosed in entelechy.

Teleology is the explanation of phenomena in terms of the purpose they serve rather than of the cause by which they arise.

Entelechy is the process of manifestation and evolution of beings : a being manifests (or realizes) entelechy when the "material" from which the being consists of, is transformed from a state of a potentiality to the state of realization (manifested in reality) due to the form that it inherited from the creator, so it (or in order to) fulfills the purpose (end goal - telos) of its existence.

It is obvious that these concepts are not compatible with the modern-current scientific way of thinking. But, by examining the definition of entelechy, I can not avoid making a comparison with QM.

In a similar way in QM all the classical concepts are, when applied to the atom ... correlated with statistical expectations; only in rare cases may the expectation become the equivalent of certainty ... it is difficult to call the expectation objective. One might perhaps call it an objective tendancy or possibility, a "potensia" in the sense of Aristotelian philosophy. In fact I beleive that the language actually used by physicists when they speak about atomic events produces in their minds similar notions as the concept of "potensia". So the physicists have gradually become accustomed to considering the electronic orbits etc. not as reality but a kind of "potensia"... the atoms or the elementary particles themselves are not as real; they form a world of potentialities or possibilities rather than one of things or facts.

Heisenberg, Physics and Philosophy.

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    Other than saying "It is obvious that these concepts are not compatible with the modern-current scientific way of thinking," this doesn't answer the question
    – Doubt
    Commented May 30 at 9:52
  • @Doubt, A principle does not have to be justified; it moulds our way of understanding and provides a context for our mind to operate. In fact the "interpretation" of the words used to justify or describe a principle, get their meaning from the principle itself. Science has it's own principles. Commented May 30 at 10:34

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