As a philosopher working in the classical European tradition, I see the importance of the distinction between being and existence in very different terms from my colleague, Allen Stairs. His claim that “not everyone sees a distinction here” might be true for a certain segment of the 20th century analytic tradition but is certainly not the case if we look at the history of Western philosophy as a whole, for which the distinction between being and existence has been the central metaphysical question. In fact, I would argue that philosophy was born as the attempt to grapple with this very distinction.

During the late 6th century BC, Heraclitus inaugurated "ontology" (the branch of metaphysics dedicated to the study of being) by focusing on the distinction between being and becoming, which roughly corresponds to that between being and existence. This correspondence was already picked up by Plato who, concerning Heraclitus’s flux doctrine, claimed the following: "Heraclitus, I believe, says that all things go and nothing stays, and comparing existents to the flow of a river, he says you could not step twice into the same river." (Cratylus, 402a). In this quote Plato tries to make sense of one of Heraclitus’s most famous fragments: “Of those stepping into rivers staying the same other and other waters flow.” The fragment brings into focus how a river remains the same over time even though the water flowing through it is never the same.

Already with Heraclitus, the distinction between being and existence invokes the epistemological issue of what can be known and how. Even though Heraclitus does not give a full account of the distinct roles performed by sense experience and reason in relation to knowledge, he certainly suggests what has become their classical alignment. While sense experience can ascertain the “existence” of the world, or its becoming, reason can describe its “being,” assumed as its essential, formal, or theoretical underpinning.

Through many variations, digressions, and permutations, the distinction between being and existence becomes once again the focus of discussion with existentialism. Anticipated by the work of Søren Kierkegaard, during the second half of the 19th century, the question regarding how to define being in relation to existence, and existence in relation to being, takes center stage in Being and Time, Martin Heidegger’s magnum opus. In his “Introduction,” Heidegger claims that the tradition has tried to make sense of the distinction between being and existence by approaching it through the wrong lens. In asking, “What is being?” the tradition has made being into just another existing entity, an impossibility given that being is itself the condition for any entity to exist.

This conclusion brings Heidegger to claim that being and existence are not only irreducible to one another but will remain inscrutable if the way of questioning each of them does not undergo a radical change. Instead of asking “What is being?” Heidegger recommends that we start from looking into the only existing entity for whom being is an all-consuming issue. Thus, in order to access being as such, the human being has essentially to question itself. In this sense, after Kierkegaard, before Sartre, and in sharp contrast to the tradition that interprets human existence in terms of rationality, personhood, or spirituality, Heidegger sees it as the only place where being is brought into view.

What fun! And indeed, it turns out that Giovanna picked my birthday to show me the error of my ways! :-)

As it turns out, however, I don't think we actually disagree about anything. Giovanna has pointed out, in effect, that folks in her tradition use these terms to mark out a distinction (or, it seems to me, a set of related distinctions) that folks in my tradition would talk about in different language. Needless to say, that's not a comment on the value of either tradition nor on the importance of the problems.

I'll confess that I don't think I have the differences here fully in view yet, but if I have it right, one distinction marked by the existence/being distinction is the difference between individual things that exist, change, have properties, etc., and the background against which the possibility of such existents makes sense. Existence, on this way of speaking, refers to the existent things, and being to this broader metaphysical background. Giovanna points to the problem of understanding how something that's always changing ( afact about existence) can nonetheless be the same thing over time (an issue about being?). This is certainly a question that analytic philosophers continue to find interesting. The kinds of problems that Plato wrestled with -- the temporal world of physical objects (existence) vs. the eternal realm of forms (being?) seems to be in the mic hre as well, and once again, analytic philosophers recognize this problem. And while I will confess to not being very familiar with Heidegger's distinction between being "present-at-hand" -- as an object for investingation -- and being "ready to hand" -- as something we simply use without the need to theorize -- also is a perfectly worthwhile distinction that anbalytic philosophers would talk about in a rather different vocabulary.

But whether any of this has anything to do with the thought that "being is the state of quality of existing" is still not clear to me.

In any case, as I said, lots of related distinctions about here, though different traditions of how to talk about them.