he's saying reality is hard to quantify.
we make qualitative judgements, from our experience - which is of necessity individual. it informed by all sorts of fragments swimming round in our consciousness.
As TS Eliot - 'these fragments i have shored up against my ruin'.
i suppose its the difference between Christian existentialists and atheist existentialists.
Both acknowledge the random nature of existence.
however the Christian existentialist looks upon the world with mysticism - searching for patterns (within and outside himself) which will imply a moral universe.