AGENT

A transliteration of the scholastic Latin agens, in general having the same meaning as mover (movens ), efficient cause, or simply cause. St. thomas aquinas regularly uses agent and efficient cause indiscriminately, often combining them as causa agens or causa movens. In dependence on Aristotle, he defines an agent as "that whereby a change or state of rest is first produced" (a quo est principium motus vel quietis—In 2 phys. 5.5). In this St. Thomas differs in no significant respect from the general scholastic tradition. At least the older scholastic tradition is also in agreement that agents in the physical order are denominated such from the effect produced by their action in the "patient," or recipient (see action and passion).

Other aspects of the scholastic notion of agent can be seen in the various assertions commonly accepted with respect to agents: "Every agent acts for an end." "Every agent acts insofar as it is in act, and according to its form." "An agent, precisely as such, is more noble than its patient or effect." "Every agent produces an effect similar to itself." "Agent and patient must exist together," and "every physical agent acts by contact" (see scholastic terms and axioms).

The principal kinds of agent recognized by the scholastics include: (1) The perfecting (perficiens ), counseling (consilians ), and disposing agents—the last being subdivided into primary (praeparans ) and secondary (adjuvans ). (2) Equivocal (or analogical) and univocal agents, depending on whether or not the agent is on the same metaphysical level as the patient; this distinction is closely related to that between universal and particular agents and that between incorporeal and corporeal agents. (3) Principal or instrumental and primary or secondary (sometimes "first" and "second") agents. (4) Natural and nonnatural agents, the latter including many other types, such as violent, chance, artificial, and voluntary; a related distinction contains necessary, chance, and free agents. (5) Finally, agents that are causes of being or causes merely of becoming, according as the effect continues to depend on the cause after it is produced or not.

Intellectual agents are included in this list, especially under artificial and voluntary nonnatural agents, but the "agent intellect" (intellectus agens ) is not. The latter is the intellectual faculty rendering abstract knowledge possible, and it is treated under intellect.

See Also: causality; efficient causality.

Bibliography: r. j. deferrari et al., A Lexicon of St. Thomas Aquinas (Washington 1948–53). l. schÜtz, Thomas-Lexikon (New York 1957).

[p. r. durbin]

a·gent / ˈājənt/ • n. 1. a person who acts on behalf of another, in particular: ∎  a person who manages business, financial, or contractual matters for an actor, performer, or writer. ∎  a person or company that provides a particular service, typically one that involves organizing transactions between two other parties: a real-estate agent. ∎  a person who obtains information for a government or other official body, typically in secret: an FBI agent.2. a person or thing that takes an active role or produces a specified effect: bleaching agents. ∎  Gram. the doer of an action, typically expressed as the subject of an active verb or in a by phrase with a passive verb.

agent An autonomous system that receives information from its environment, processes it, and performs actions on that environment. Agents may have different degrees of intelligence or rationality, and may be implemented in software, hardware, or both.

Software agents operate in symbolic environments, and perceive and act upon strings of symbols; examples include personal assistant agents that enhance and customize facilities for computer users, and data mining agents that search for interesting patterns in large databases. In a distributed system, the agent for a remote procedure call is in a different computer from the caller; its environment is the network and the procedure body. A robot (see robotics) is an example of an agent that perceives its physical environment through sensors and acts through effectors.

AGENT. In grammar, the person or other being that instigates the happening denoted by the verb: Jenny in the sentences Jenny has written me a letter and Jenny made Henry angry refers to the doer of the action or the causer of the event. In English, the semantic role of the subject in active constructions is typically agentive, but not exclusively so: books in These books sell well is not the agent but the affected. In a passive construction, the agent may be represented in an optional by-phrase: Anita and Michael were mugged (by some louts) on their way home last night. The term agent or agentive is used in case grammar for one of the sematic cases.

agent XV. — L. agēns, agent-, sb. use of prp. of agere do; see -ENT.
So agency XVII.