The Four Causes Defined

Principle: "that from which something proceeds in any way whatever" (Fr. William Wallace, OP, The Elements of Philosophy [Wipf & Stock, 2011], 44, §16.7); "the intelligible framework or conditions of change" (John Deely, Medieval Philosophy Redefined, 143).

Three principles of change in Aristotle's thought: 1) form; 2) matter; 3) privation.

Cause: "that from which something proceeds with a dependence in being" (Wallace, 44, §16.7; see also 100, §35.1) or that upon which something depends for its being.

Condition: "that which makes possible, makes ready, or prepares the way for an efficient cause to act, or for its action to be efficacious" (101, §35.3).
-the condition in which an obstacle is removed that "would otherwise block the agent's activity or render it ineffective" is called the removens prohibens.
-a condition that is an absolute requirement for the cause to function, a necessary condition: conditio sine qua non.

Occasion: "the opportunity for a cognitive agent to exercise its causality" (102, §35.4).

Four Causes (and Medieval subdivisions):

Material (Matter): "the intrinsic determinable principle that receives its actuation and determination from form" (103, §35.6); "that upon which the agent acts" (Deely, 140, fn. 6).

Efficient (or Agent or Productive): "the productive or transient action initiated by an agent [where] an agent be understood as anything capable of initiating a motion or a change" (Wallace, 104, §35.8).
Kinds of efficient causes:
1) Essential vs. Coincidental
2) Total vs. Partial
3) Principal vs. Instrumental (instrument: "something from which an effect flows by reason of its subordination to a principal efficient cause, to which the instrument ministers and by which it is moved" [ibid.]).
4) Primary vs. Secondary
5) Perfecting vs. Disposing
6) Natural vs. Non-Natural (e.g. violence, chance, artificial, voluntary)
7) Univocal vs. Equivocal vs. Analogical (depends on "metaphysical level" of the agent vs. patient)
8) Universal vs. Particular
9) Corporeal vs. Incorporeal
10) Agents that cause being vs. agents that cause becoming

(Intrinsic) Formal: "the intrinsic principle of existence in any determinate essence" or "the intrinsic determinant of anything that is determinable" (102, §35.5); "the result in or response of the material correlated with the action of the agent" (Deely, 140, fn. 6).
-Extrinsic Formal Cause (Exemplary or Ideal): that form which is introduced into matter "by an intelligent agent" according to a pattern or plan (ibid.).
1) Exemplary vs. Specificative (or Objective): that which specifies "cognition as an awareness of this rather than that object or aspect of an object" (ibid.).

(Intrinsic) Final (or Teleological): "the full development of the substance or the completion of the process itself," where "the end itself may be defined as that for the sake of which something exists or is done, or that for which an agent acts or action takes place"; "it is said to be first in the order of intention and last in the order of execution or activity"; also called the "cause of causes (causa causarum)" (Wallace, 105, §35.10); "the [intrinsic] pattern of development which an effect once produced exhibits over time" (Deely, 104, fn. 6).
-Extrinsic Final Cause (Exemplary/Ideal): "the determination or form of an effect as this is preconceived by an intelligent agent," which is "extrinsic to the effect and exerts its influence mainly as an idea in the intentional order" (Wallace, 106, §35.11); "the intention according to or purpose for which [an agent]" forms a material structure (Deely, 140, fn. 6).