of esse in the sense of esse essentiae, but it certainly does not have merely the function that Mill intends when he equates "is" and "means."
A fourth example. taken from Mill, reads "The centaur is a fiction of the poets." According to Mill this sentence is purely verbal. It is for him an example of the existence of propositions which do not assert being in the sense of existence but are explanations of words. If we examine this proposition more closely. it indeed appears that something is asserted in it, namely, what the centaur is. But this whatness which is asserted of the centaur expresses, precisely. a way of the centaur's being. Its intended meaning is that things like centaurs exist only in an imaginary way. This proposition is an assertion about existence. If this proposition is to be understood at all in its restrictive form and signification, existence in the broadest sense must in a certain way be thought in thinking it. Its intended meaning is: Centaurs do not exist actually but are only inventions of the poets. This proposition is, again, not a verbal judgment: the "is" also does not signify existence in the sense of being extant, but it nevertheless expresses a certain mode of being.
All these propositions we have mentioned contain still another meaning in their "is," for in all propositions as uttered their being-true is implicitly intended. This is the reason why Lotze lights upon the theory r1 the subsidiary thought. How is this being-true connected with the "is" itself? How are these differing meanings of "is" concentrated in the unity of an assertion? The answers must be given by the positive analysis of the proposition, so far as we can accomplish it at this stage of our considerations.
We may now offer this brief outline of all the different interpretations of the copula:
First. Being in the sense of the "is" has no independent signification. This is the ancient Aristotelian thesis: προσμένῃ σύνθεσιν τινα-it signifies only something in a combinatory thinking.
Second. According to Hobbes, this being signifies being-the-cause of the combinability of subject and predicate.
Third. Being means whatness, esse essentiae.
Fourth. Being is identical with signifying in so-called verbal propositions or else it is synonymous with existence in the sense of being extant, esse existentiae (Mill).
Fifth. Being signifies the being-true or being-false that is asserted in the subsidiary thought of every judgment.
Sixth. Being-true—and with this we return to Aristotle—is the expression of an entity that is only in thought but not in things.
In summary we may say that the following are implied_in the "is": (1) being-something [Etwas-sein] (accidental), (2) whatness or being-what [Wassein]