Preparation for the 5 March 2019 Session

Resultado de imagen para act and potency"Translation" of some of the terms to ordinary language, just as a first intuitive approach to the concepts (not a full academic explanation) of Aquinas's De ente et essentia, I-III 
  • ​"being" = a verb, the act of being (essse); or = something that "is" in the sense of actively being (ente); 
  • "essence" = that which something is (essentia); all things "are" (have being, esse), each is  a "being" (ente); but how do you distinguish between one and the other? By their "essence" or the what they are (a tree, a human person, etc.);
  • "act" = the principle of "movement" ​​metaphysically understood (from possibility to reality, from capacity to actual perfection);
  • "potency" = the principle of "limitation" or contention of act (possibility before it becomes real, capacity before it reaches perfection). 
  • "substance" = a "proper" being (when "being" means "ente," see above);
  • "accident" = a feature of a substance, something that can or cannot be in the substance without the substance losing what it is.
  • "nature" = the principle of (metaphysical) movement of something, according to what it is.
  • "genus" = a family of species.
  • "species" = what something is, its "quiddity" or essence.
  • "quiddity" = from the Latin interrogative "quid" or what (is)? Used as equivalent to nature, form or essence depending on the context.
  • "form" = the principle of actuality making a being (ente) to have a specific nature. 
  • "matter" = the principle of limitation that makes possible for material beings (entia) belonging to a species to be many. 
An example. A horse is a being (ente), because is something that has act of being (esse). Before we say anything about it, we take for granted that it is. Its essence (essentia) is to be an animal that eats oats and alfalfa, drinks water, neighs, runs, etc. A foal is a mature horse in potency (potentia), if you train it and care for it to develop to its full ​perfection (actus) or actuality, one day it will run as fast as an adult horse. It is of the substance (substantia) of the horse to have four legs, not one hundred, but whether ​​it's being brown is an accident (accidens): it could be white and still being a horse. It belongs to its nature (natura) to neigh and to run, but not to fly. "Horse" is a species of the genus "animals". The matter of a horse is this matter that makes this horse different from all the other horses. Its form is the nature of a horse that this particular horse shares with all the other horses members of the same species. The essence of a horse comprehends its form and matter. And for a horse to exist essence is not enough it needs the act of being (esse). 

It can be shown the possibility non material beings or "intelligences"; they can't be differentiate from one another by matter, so each of them is a species constituted of one individual. Still intelligences or non-material or spiritual beings are composed of essence and act of being (esse).

Some clarifications requested by group members:

The categories mentioned in the reading refer to what we can say about things, substance and the nine accidents. Substance has act of being in itself and therefore possesses some independence. The accidents are quantity, quality, relation, location, time, position, habit, action and passion and they don't have their own act of being but live in another. You can find a simple explanation here and a comprehensive one here.

To better understand paragraph number 18, St Thomas is saying that through the form something acquires not only the act of being, but the act of being in a certain, specific way. The form "whiteness" causes something concrete to be white. But the key to understand the paragraph is the conclusion: "It remains, therefore, that the word 'essence' in composed substances signifies that which is composed of matter and form". Not only act of being, but matter and form which make for instance a horse not just any creature or just any horse, but this concrete brown, 4 year old horse that I'm riding.   

Prime (undesignated) matter is the principle of material potentiality to become anything, but it's pure indetermination. Designated matter (materia quantitate signata) means the matter that has been actualised in a certain way, i.e. a matter that has received a form to become something (eg a horse). 

Finally, in paragraph 28 St Thomas is not saying that the human being has two natures (as we say of Christ assuming the human and the divine nature), or that he has two different essences in one (eg a frog and an eagle). The key to understand the paragraph is "perfection". So the essence of humans implies both the sensitive perfection (shared with animals) and the intellectual perfection (shared with spiritual beings). But he is speaking about human beings as being one essence only.