The universal thus has two aspects: on the one hand, the nature which has its origin in single things and which is grasped by the intellect by means of the abstractive process; on the other hand, the intention of universality which the nature follows from and in intellective apprehension*. The nature or essence possesses therefore two ways of being: one singular in the existing reality, and one universal in the knowing intellect. Now intentional identity wouldn't be possible between these two ways if they did not have in common the same nature. Therefore we should add to these two ways of being the nature in itself, which is not a third way of being, but rather what is common to both ways of being, leaving being (in the thing or in the intellect) out of it. Thus we are able to distinguish the so-called "three states of nature"**:
secundum rationem propriam: Natura secundum se [α]
(according to its own definition)
secundum esse quod habet in hoc vel in illo: natura in singularibus [β]
(according as it has being in this or in that)
natura in anima [γ]
[α] The natura secundum se (nature as it is in itself) is the nature considered independently of any existence (whether in the thing or in the soul); therefore it comprehends only the essential components of the essence in question. For example, human nature considered in itself includes only the essential predicates of humanity (being, substance, bodily, living, sensitive, rational), to the exclusion of the individual predicates and of existence.
[β] The natura ut in singularibus (nature as it is in single things) is the nature considered insofar as it exists in the concrete single being, like Peter or Paul. This 'state of nature' includes real existence and excludes intentional existence. Therefore the nature is found in this case in an individual way and not universal.
[γ] The natura ut in anima (nature as it is in the soul) is the nature considered as it exists in the human intelligence which knows abstractively, for example in the notion of "man". This 'state of nature'is an abstraction from the individual predicates and singular existence, like [α], but adds to [α] the intentional way of being proper to it which is universality.
The universal consists only in [γ], since [β] is singular by definition, while [α] neither includes nor exludes predicability***.
* Cf. Sn 1, 19, 5, 1, c: Humanitas enim est aliquid in re, non tamen ibi habet rationem universalis, cum non sit extra animam aliqua humanitas multis communis; sed secundum quod accipitur in intellectu, adiungitur ei per operationem intellectus intentio, secundum quam dicitur species.
** On this doctrine, cf. EE, 3, nn. 16 - 18; SA 2, lect. 12, n. 378.
*** In this regard, cf. EE 3, n. 18: ?Non tamen potest dici quod ratio universalis conveniat naturæ sic acceptæ; quia de ratione universalis est unitas et communitas. Naturæ autem humanæ neutrum horum convenit secundum suam absolutam considerationem. Si enim communitas esset de intellectu hominis, tunc in quocumque inveniretur humanitas, inveniretur communitas; et hoc falsum est, quia in Socrate non invenitur communitas aliqua, sed quidquid est in eo est individuatum.
EE 3, n. 18
Nevertheless, the nature understood in this way is not a universal notion, because unity and commonality are in the notion of a universal, and neither of these pertains to human nature considered absolutely. For if commonality were in the concept of man, then in whatever humanity were found, there would be found commonality, and this is false, because no commonality is found in Socrates, but rather whatever is in him is individuated.
A translation of Fr Alain Contat's Logica