We know what we know and we don’t know what we don’t know. That we can be rather sure of. But think about this question: “What is the ratio of what we know to what we don’t know?”
That ratio, it would seem, is part of what we don’t know. If we think about everything that humans currently know – e.g. the information that fills the great libraries -- most of us should admit that the ratio is rather small. And even if we are among the most knowledgeable of people, the ratio is still likely not very large.
Another question: “What is the ratio of everything that humans currently know to everything that could possibly be known?” There are cosmological theories that posit countless numbers of other universes. If these theories are true (whether they are or not being another thing we don’t know), then the ratio is possibly infinitely small.
But to narrow things, what if we just consider the visible portion of this universe? Well, there might be numerous solar systems with intelligent beings, some possibly considerably more so than us. Currently we know nothing of their worlds; currently we don’t know if such worlds exist. So even here the ratio is possibly very, very small.
We could get even narrower and consider just this earth; we would seem to know quite a bit about that. For instance, it is probably the case that the known and cataloged species of plants and animals currently living are a fairly large ratio of all the currently existing species. But it has been suggested that for every currently living species there have been a thousand that are now extinct. If this number is anywhere near being correct, than the number of extinct species we know anything about would seem to be a rather small percentage of the total. So the ratio of what we know about the living species that have comprised the earth’s biosphere throughout its history compared to everything there is to be known is again very small.
At this point a person may throw up her or his arms and say, “well I know what I need to know!” But how would a person know this since we don’t know what we don’t know? Most of the people I know seem to me to be missing some important pieces of knowledge about quite basic things, and they also seem to be blithely unaware of it.
Socrates, who was considered by many a very wise and knowledgeable person, famously stated that “I know that I don’t know.” From the foregoing discussion, I think this is something of which each of us could be reasonably sure.
To know that we don’t know seems to be negative knowledge, and should we not be more concerned with positive knowledge? Perhaps, but anyone who spends time reading comments on the Internet might wish that more people understood the limits of their knowledge. (Why are there so many people who passionately believe in the most un-belief-worthy notions?) I would suggest that having at least some sense of the limits of ones knowing is actually a very positive kind of knowledge.
You need to know a great deal, I would suggest, to truly know that you don’t know. One has to spend a lifetime trying to know if one is going to have any creditability in saying “I know that I don’t know.” So if the person who says “I know that I don’t know” actually knows a lot relative to most, is this person a liar? Or is it a recognition that all knowing isn’t equal? There are the answers to big questions and answers to small questions, and while Socrates and most of us probably had plenty of the later, it is in relation to the former that our un-knowing is significant. But here again, do we know what the really significant questions are?
The philosopher Ludwig Wittgenstein wrote: “what can be said at all can be said clearly, and what we cannot state clearly we must pass over in silence.” I don’t necessarily think this statement is true and later in his life Wittgenstein apparently became doubtful about this himself. But I do think it is sometimes wise to be silent. Silence, like the knowing of one’s ignorance, might seem the negation of knowledge, but is it? Perhaps I’ll just shut up and listen to what the silence says.