2. Analytical Introduction (10)

3.1.1. The ens rationis, genus of the logical being

a) Definition

The expression ens rationis signifies an entity that depends on reason for its being. But this dependence can be taken in three ways:

1 effectively: something depends on reason insofar as it comes from it through efficient causality, as the acts and products of the mind (for example judgment and the proposition considered as a product of judgment).
2 subjectively: something depends on reason insofar as it is based in it, like a material cause, as the intellectual habits (for example the habitus of logical science).
3 objectively: something depends on reason exclusively insofar as it "exists" before it as an object, without it having in se any real ontological consistency, as the relations between concepts (for example the attribution of a predicate to a subject).

The being of reason in the strict sense, which is of interest to us here, corresponds uniquely to the third meaning, while the first two meanings are in reality of real beings. We can define it in this way with John of St Thomas:

ens habens esse obiective in ratione, cui nullum esse correspondet in re.
Ars logica, II, q. 2, art. 1, 285 b 14-16

The essential characteristics of a being of reason consist therefore in the absence of ontological positivity, its "being" reducing itself to purely being an object. For example, light is a real being, which can also be conceptualized by the mind, whereas darkness, per se, refers to nothing real, but only the privation of light, for which reason it is a being of reason.

One can see therefore that

The being of reason is that which exists only through and in the awareness we have of it, insofar as it is a construct of the mind, whereas real beings are those which exist independently of the awareness we have of them.

b) Division

The notion of ens rationis is divided, for the purposes of the present subject, in two different ways:

1. division based on the subject to which the being of reason is attributed:
[-a] without foundation in things
[-b] with foundation in things

[-a] implies a real foundation to which the being of reason is attributed, for example the air by darkness.
[-b] has no real foundation at all to which the being of reason is legitimately attributed, for example the unicorn or chimera.

2. division based on the object itself conceived but nonexistent in reality:
[-a] negation
[-b] relation of reason

In fact, the notion of ens rationis consists formally in its opposition to real being, that is in its incapacity to exist**. Now such a notion can either be something purely negative, or something positive. If negative, we have negation; if positive, we have only relation, because it is said only in regard to some other thing, without implying any absolute positivity, which would consist of real being. An example:
[-a] blindness, privation of sight; darkness, negation of light.
[-b] being seen by something, relation to the one who sees; being predicated, relation of a concept to some other in a proposition.


c) Application to logic

By these distinctions, we can explain the genus of being which formally specifies logic. It consists in the relations of reason which the mind constructs on coming to know reality and which therefore are founded in it. We must state more precisely what formally consitutes these relations and distinguishes them from other things, that is their specific difference.



** In this regard, see QDV 21, 1, c:

What is merely conceptual, however, can be of only two kinds: negation and a certain kind of relation. Every absolute positing signifies something existing in reality. Thus to being, the first intellectual conception, one adds what is merely conceptual—a negation; for it means undivided being. But true and good, being predicated positively, cannot add anything except a relation which is merely conceptual.

For a theoretical justification of this division of ens rationis, see John of St Thomas, Ars logica, II, q. 2, art. 1, 287 b 13 - 288 a 39