Can and its equivalents in other languages is one of the first verbs we learn, and one we use every day. One should think then, that we know well and true what the word means, but perhaps exactly because its use is so common and automatic, we rarely reflect upon it. And as a consequence, more is added into the word than can be allowed – and our view of the world is much distorted by our ingrained understanding of can.
The most common meaning of the word is to describe that something is possible; I can stand on my hands, the sun can burn your skin, and so on. And so we run into the word possible, which is again misunderstood. We all know the dictionary meaning of possible; that it is neither certain nor impossible that something will happen. But herein lies a tremendous assumption: that there exists other possibilities than certain or impossible.
Sitting in this room where I write, I can say that is possible that a person comes into the room during the next 5 seconds. The door is not locked, and I have no way of knowing what is outside; thus I can neither say it is certain or impossible that someone will come. Simultaneously, a person standing outside can observe that there are no people around, and conclude that it is impossible that someone enters the room within the next 5 seconds.
However, the occurrence of an event cannot be impossible to one observer and at the same time possible to another. Of course, no one considers the situation in the previous paragraph to present a paradox, because sitting in the room saying it is possible, we all know that I only say that it is possible as far as I know.
Possible is only a description of our knowledge and imagination, not of the universe. Followingly, can also pertains only to our knowledge and imagination, and not necessarily to reality. Considering such examples as above, most will say that it is clear that this is what the words describe. Still, we use the words in a more definite manner – as if they imply there is a real probability, independent of our knowledge, that something will happen, or as if there was a real possibility something could have happened.
Life would be tedious if we would philosophize about every word whenever we speak, but when these definite implications are attached to the words even in serious discussion one risks misunderstanding a great deal.
Indeed, just the idea that there is a real probability that something may happen that does not depend on knowledge has deep philosophical implications about the nature of the universe. For it implies that there are events, the occurrence of which cannot be predicted by the hypothetical knowledge of anything – which means the event must be, to some extent, independent of everything else. That is, the universe cannot be deterministic, but partially random.
But even about events which occurrence we think of as completely deterministic we use can as a statement about the universe, and not of our knowledge. In debates about religion, one can hear arguments from the non-religious side of the type “why would a good God create a universe in which an asteroid/virus/bacteria/etc can wipe out all human life?”. Considering can only as a description of our knowledge and imagination, such arguments do not seem to argue for much at all.
It seems our understanding and use of can is a great contributor to our philosophical understanding of the universe – and it would be interesting to study what is the order of things here; does our way of thinking about events follow our deep-rooted understanding of can, or vice versa?
Without diving deep into the ever-controversial topic of free will, is not a common argument and motivation behind it exactly that we can? “I could have done that”, “I can do this”. Truthfully, the statement “I could have done that” says nothing more than that “I” have no knowledge that excludes the possibility that “I” could have done “that”.
To say that we do not have the knowledge to conclude or exclude the occurrence of an event is a conclusion itself; we do not know. From this, nothing can be inferred about determinism, randomness or free will. To say that something may happen or could have happened in some other, mysterious sense, however, directly implies definite information about these things. For if the universe is deterministic, “may happen” does not make sense as anything else but a description of our knowledge and imagination, and “could have happened” could not have happened.