In Basic Concepts, a series of lectures given in 1941 by Martin Heidegger, we are told that to the whole, or entirety, of beings belongs actuality, possibility and necessity. Heidegger notes that “The realm of beings is not identical to the domain of the actual…we mean more than the ‘actual’ when we says ‘beings’. Indeed the actual is perhaps not at all the standard for beings. And whenever one demands closeness to the actual for human life, the ‘actuality’ that is really meant is not what is simply present, but what is planned, not what is mastered, but an unspoken claim to power. The oft-mentioned ‘actual’ is not the actual, but the possible. Thus we never think ‘beings’ as a whole as long as we only mean the actual. Henceforth, if we earnestly think beings as a whole, if we think their being completely, then the actuality of the actual is contained in being, but also the possibility of the possible and the necessity of the necessary.” The point of the last sentence is that the notion of being contains within it the notions of actual, possible and necessary. The claim of the above quotation could be illustrated as follows:
The question comes to mind, what does Heidegger mean when he uses these terms? When he explains what is meant by actual, he says, “the currently actual, which affects us and which we stumble upon: the happenings, the destinies and doings of man, nature in its regularity and its catastrophes, the barely fathomable powers that are already present in all motives and aims, in all valuations and attitudes of belief.” By actual he means what presents itself to us as present, not merely as mind-independent, but also, the present attitudes and beliefs. By possible he means, “the not yet actual.” He says that “The possible also ‘is’, its being simply has another character than the actual.” We are not told what he means by necessary, though it is likely that he simply means what must be.
Pushing his thoughts a little bit further, and coming back to the quote above, what is he trying to say, when he says that the notion of actual does not exhaust the notion of beings? In order to understand this we need to understand the distinction that he makes between being and beings, which seems vaguely similar to Aquinas’s distinction between essence and existence. He notes that “When we say ‘beings are,’ we distinguish each time between beings and their being, without noticing this distinction at all.” Why is this distinction important? It seems, when we consider the notion of “possible beings” we are obliged to say that we do talk about things that are not yet, but which could be or could have been. We say things such as “I could have been an entertainer.” “I could have been a gangster.” “I hope to a become philosopher.” “I could be wrong.” “A house will be built on this land.” However, though we can talk about these possible beings, they do not as of yet exist, in other words, they are not actual, they are not present and they are not “there”. It seems, however, that, in a sense, even these possible beings cannot be talked about unless there is something that grounds or founds their being. Here the distinction between being and beings becomes obvious. These possible beings do not, in a sense, have being. Perhaps we could say it another way, the being of possible beings is dependent on something that is actual. If there is no being-there, then there can be no possible being. Possible being is dependent on Actual being, and in a sense, is included in it. Possibility is included in the notion of what is actually there. Can we then say that Actual being includes, in a sense the being of what is possible? That would change our chart a little bit.
This leaves us with the notion of the necessary. The necessary seems to be, in general, placed in opposition to the possible. That is, what is possible could be, but what is necessary must be. If this is the case, then the necessary is a qualification of the actual – what is. In other words, what is actual is also, by the fact that it is, necessary. This is the notion that is used in the claim that a necessary being is a being that exists in all possible worlds, or, in other words, a necessary being is a being that is actual (is there, is present) in all possible worlds. As such, the necessary is a description or qualification of the actual. The conception of necessary is frequently contrasted with the concept of contingent. A contingent being could be described as a being that is but possibly is not, or is not, but possibly is. It’s being actual (there or present) depends upon some other being that is actual (there or present). Contrasted with such a being, a necessary being contains within it the principle of its own being (actuality, there-ness, present-ness). Again, following this conception it seems that the notion of necessary (as well as the notion of contingent) is a qualification of the notion of actuality. We might, therefore, modify our chart again:
If we assume for the moment that these three notions are the only possible qualifications of being, then, it seems that the notion of actual, simply is the notion of being. We could put it this way, necessarily, x is (or in other words, x has being), if and only if, x is actual. Thus we would modify our chart again as follows:
Some objections could be imagined. What about possible worlds, they have being, but are not actual, therefore, they would be excluded from being if being simply is actuality. In response to this objection we could return to the distinction, that we noted above, between being and beings. It seems that, properly speaking, possible worlds are only possible beings that have their being in the mind of the philosopher, and whose possible being is dependent on what actually is (is there, is present). We might call possible beings that are in the mind of a thinker, following the medieval philosophers, a being of reason. A being of reason only has being in the mind of the person that is thinking it, and insomuch as it is being thought about, it is actual (it is there, it is present) – intellectually. Therefore, possible beings fall under the notion of actuality, metaphysically and epistemologically.
Martin Heidegger, Basic Concepts, trans. Gary E. Aylesworth (Bloomington, IN: Indiana University Press, 1998), 22.
Note, in this article, I am simply taking off from a very small section of Heidegger’s work, and thinking about the notions that he articulates, regardless of whether or not he actually ends up agreeing with this initial position. Much of these observations are certainly inspired by Aquinas's De Ente et Essentia.
Some philosophers think that possible worlds are actually existent abstract objects. I would suggest that if it is possible for an abstract object to exist independently of any mind, then, in order to be consistent with our terminology, as defined above, possible worlds are actual. This is a subject that is frequently debated by the very best metaphysicians.