David Oderberg, in his book Real Essentialism (Routledge Studies in Contemporary Philosophy, Vol. 11), describes the metaphysical system that derives from Aristotle, Thomas Aquinas, and their students. This system is the closest thing to explaining our common sense knowledge of the world around us that I have ever seen. It is sometimes called classical Christian metaphysics or Aristotelian-Thomistic metaphysics.
If it embodies the best common sense, then why write about it? Everybody should be agreed! It turns out that every one of its tenets has been and continues to be attacked by philosophers who propose competing metaphysical systems. As you read through the presuppositions for real essentialism below, keep in mind that every point is disputed by somebody in the academic, philosophical world.
Oderberg offers five presuppositions for real essentialism:
First, there is a real world , by which I mean a world that is wholly objective. . . . Of course there are many dimensions of contrast for the term ‘real’ – real v. fictional, real v. artefactual, real v. imaginary and the like – and the essentialist incorporates all of these distinctions into his ontology. But the overall position he holds is that there is a real world, and that the things in it are all real in the sense that they are beings of one kind or another and their being is not a matter of opinion or conjecture.
Secondly, the reference to being indicates that the real essentialist starts from the classic Aristotelian position that metaphysics is the study of being qua being: being in all its manifestations and varieties, classified according to a suite of concepts and categories that derive from the Aristotelian tradition. . . . Real essentialism takes nature seriously, and whilst it may countenance the existence of the immaterial – as I think it should – it does not reduce or refer nature as it is in concrete physical reality to a realm of the immaterial that is supposed to be its ultimate ontological ground.
Essences are real, they encompass all kinds of being and, thirdly, they are knowable. The essentialist is committed to the view that the human mind can come to know the essence of things. Knowledge of the truth just is the conformity of the mind to the way things are, and so knowledge of essence is the conformity of the mind to the natures of things. The knowledge is frequently only partial and incomplete, but it is no part of the real essentialist worldview that humans can always achieve complete, adequate knowledge of the essences of things. This not a counsel of despair but an encouragement to the increase and improvement of knowledge.
Fourthly, real essentialism holds that knowledge of essence is captured by means of real definition. As Fine puts it, ‘[ j]ust as we may define a word, or say what it means, so we may define an object, or say what it is’ (Fine 1994a: 2). The prejudice against real definition is a deeply held one, going back to the roots of empiricism. Yet it is hard to see why the concept is unacceptable. Indeed, since defining a word is best seen as giving the essence of a kind of object (the meaning), the opponent of real definition who at least concedes that we can define words has already conceded the principle that one can define objects of a certain kind; if that kind, why not others ? . . . To define something just means, literally, to set forth its limits in such a way that one can distinguish it from all other things of a different kind. . . . Putting the point again in Aristotelian terminology . . . , to give the definition of something it to say what it is, to give the ti esti or to ti e-n einai of the object. Put simply, the real essentialist position is that it is possible to say correctly what things are.
Fifthly, the real essentialist holds that the world is orderly and hence that things are classifiable, a point heavily emphasized, and rightly so, by Ellis. Describing the world accurately requires one to be able to classify the things within it into kinds of being. This does not depend on there being multiple examples of any particular kind, for even if each thing that existed were the only one of its kind it would still be classifiable as a member of some kind or other. . . . The real essentialist, however, is concerned primarily with classification not according to some real dimension or other, but according to what objects are in their entirety. This is given by the form of the object as a whole, and this too is multiply instantiable.
Let’s simplify further to the following five statements:
- There is a real world.
- The metaphysician should study the world as it is.
- Essences are real, they encompass all kinds of being, and they are knowable.
- It is possible to say correctly what things are.
- The world is orderly and the things in it are classifiable.
From these five points is where the real essentialist starts. Again, all of these statements seem blindingly obvious to me, but philosophers at universities that you are sending your kids to might disagree. All I can say is, “Beware.” Once you start denying these five points, you are on a trajectory of intellectual chaos and confusion.