From an address presented by Peter Kreeft to the CiRCE Institute Annual Conference in July 2013, and posted in full on the Imaginative Conservative website:
There are at least 19 different kinds of judgment that we should distinguish. I’m sorry I could not find a 20th, to match the number of digits on our fingers and toes. But 19 does match the digits of Frodo Baggins, one of my heroes. (I’m sure you remember Frodo of the Nine Fingers, and Gollum of the Eleven.) The importance of the topic wisely assigned to me—judgment—is obvious. For one thing, making judgments is a privilege of persons only. For another thing it is necessary, both to live well on earth and to enter Heaven.
I will say one thing about each of these 19 kinds of judgments. It may not be the most important or most fundamental thing that can be said about them, but it will be a point I believe is important enough to take two minutes, of a captive audience’s precious time to think about.
The first kind of judgment is judgment as such, judgment in the abstract. By this I mean the logical form of judgments: the affirmation or denial that a predicate belongs to a subject, that some state of affairs is true or is not true. This is “the second act of the mind” in traditional Scholastic logic, and the only one that contains truth. The first act of the mind, simple apprehension or conception, does not contain truth because it merely conceives of concepts, which are neither true nor false, but are the raw material or contents of true or false judgments. Thus neither the concept “apples” nor the concept “fruits” is true or false, but the judgment “Apples are fruits” is true. The third act of the mind, reasoning, moves from the presupposed truth of one or more judgments, as premises, to the truth of another judgment, as the conclusion to be proved. Concepts tell us what, judgments tell us whether, and reasoning tells us why. We understand essences in concepts, existence in judgments, and causes in reasoning.
Because concepts attain only essences while existence is attained only in judgments, this essential logical structure of thought implies the distinction between essence and existence, one of the most important principles of metaphysics and the basis for Aquinas’ best proof for the existence of God: the proof from contingent beings to a necessary being—that is, from the premise of the existence of beings whose essence is not existence to the conclusion of the existence of a being whose essence is existence, as the only adequate answer to the question of why these other existing things exist. If their existence does not come from within their own essence, it must come from outside, from a cause. Only a Being whose essence is existence can explain the existence of beings whose essence is not existence, as their cause. Only a Being that explains itself can explain the beings that do not explain themselves.
The distinction between essence and existence, and between concepts and judgments, also explains why St. Anselm’s famous “ontological argument” is invalid: it confuses essence and existence, treating existence as an essence, a “what”, or a property. My point here is how centrally important it is that only judgments attain ontological existence and logical truth. When we investigate concrete particular judgments rather than the universal, abstract, logical form of judgments, we find that they are made either by humans, or angels, or God, who are the only three kinds of personal beings we know, except for lawyers and Deconstructionists.