Thomistic Philosophy
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Thomistic Metaphysics
Act and Potency

ACT : (a.k.a. ACTUALITY) ANY ENTITY WHICH PERFECTS A THING IN ITS BEING   Click to Expand ⤵

  1. Entitative Act (a.k.a. Act of Existence or Existential Act)
    That which makes a being exist
  2. Formal Act (a.k.a. Act of Essence or Actuality of Essence)
    That which makes a being what it is   ⤵
    1. First Formal Act (a.k.a. Substance)
      That which makes a being what it is in itself (or by itself)
    2. Second Formal Act (a.k.a. Accident)
      That which makes a being what it is in another
POTENCY : (a.k.a. POTENTIALITY) THE CAPACITY OR APTITUDE FOR SOMETHING   Click to Expand ⤵

  1. Objective Potency (a.k.a. Possibility)
    The capacity of a nonexistent being for existence   ⤵
    1. Intrinsic Possibility (a.k.a. Absolute Possibility or Internal Possibility or Negative Possibility)
      The capacity considered absolutely in itself
      (e.g. the existence of a chair is intrinsically possible, whereas the existence of a square circle is intrinsically impossible)
    2. Extrinsic Possibility (a.k.a. Relative Possibility or External Possibility or Positive Possibility)
      The capacity considered relative to another being's power to produce it   ⤵
      1. Natural Possibility (a.k.a. Physical Possibility)
        The capacity considered relative to another being's natural power to produce it
        (e.g. the existence of Shakespeare's Works being produced by a human is extrinsically possible, whereas the existence of Shakespeare's Works being produced by the color blue is extrinscially impossible)
      2. Moral Possibility
        That which can be produced according to a rational agent's will (the agent in this case must be a rational being)   ⤵
        1. Morally Advisable Possibility
          A morally good possibility which can be produced by a rational agent
          (e.g. healthy eating is often an morally advisable possibility, whereas murdering an innocent person is not)
        2. Possibility Lacking Grave Difficulty
          A possibility which can be produced by a rational agent that does not involve considerable moral difficulty
          (e.g. for a typical person, swimming across a small pond is a possibility that lacks grave difficulty, whereas swimming across the Atlantic Ocean is not)

  2. Subjective Potency (a.k.a. Physical Potency or Real Potency)
    The capacity of something already existing for another act or perfection   ⤵
    1. Active Potency (a.k.a. Operative Potency)
      The capacity for doing something
      (e.g. a horse has the active potency for galloping)
    2. Passive Potency (a.k.a. Receptive Potency)
      The capacity for receiving something
      (e.g. a horse has the passive potency for being whipped)