Source: Ch 3, Section 2, Critique of Pure Reason, by Kant, translated by Norman Kemp Smith

I should have hoped to put an end to these idle and fruitless disputations in a direct manner, by an accurate determination of the concept of existence, had I not found that the illusion which is caused by the confusion of a logical with a real predicate (that is, with a predicate which determines a thing) is almost beyond correction. Anything we please can be made to serve as a logical predicate; the subject can even be predicated of itself; for logic abstracts from all content. But a determining predicate is a predicate which is added to the concept of the subject and enlarges it. Consequently, it must not be already contained in the concept.

predicate = [with object] 1. {Grammar & Logic} state, affirm, or assert (something) about the subject of a sentence or an argument of a proposition

I recast user John Lawler's comment: Denote A a human agent, P a predicate; X the argument of P.
A predicates P of X   =   P is predicated by A of X   =    Say( A, P(X) ).

Yet I remain confused. I don't see any human agent here, How do you determine/deduce the meaning of the bolded? How can a subject predicate itself?

Footnote: This bolded phrase features as the first Example Sentence at ODO.

  • It is what it is. Satellites are out tonight; let x equal x.
    – TimR
    Feb 3, 2015 at 20:09
  • 1
    a subject can be predicated of itself ≠ "a subject predicate[s] itself"
    – TimR
    Feb 3, 2015 at 20:19

1 Answer 1


Kant's sentence is a passive, so neither the predicating Agent (John Lawler's A) nor the preposition by which marks it is required to be present. In John Lawler's construction

P is predicated by A of X = Say( [A,] P(X))

Kant puts forward an agentless construction in which the "subject" of the predication, X, is also the predicate, P:

X is predicated of X ... for example
A rose is a rose is a rose.
Boys will be boys.
Whatever will be will be.

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