Possibility… is to human existence what vowels are to speech. To live in pure possibility is like an infants utterance of vowel sounds, which fail to express something that is definite and clear. Vowels alone do not make for articulate speech, although without them nothing can be said at all. Similarly, “if a human existence is brought to the point where it lacks possibility, then it is in despair and is in deeper every moment it lacks possibility.” One cannot breathe without oxygen, but it is also impossible to breathe pure oxygen. Possibility is a kind of spiritual oxygen that a person cannot live without, but one cannot live on pure possibility either.
C. Stephen Evans, Kierkegaard: An Introduction