What is Alfred North Whitehead trying to say in the following quoation “Religion is what man does with his solitariness”.

Alfred North Whitehead was a British thinker who believed
that it was important to modify traditional views of what religion meant.  It is in this
context that you should understand this quote.

If you look
at the essay from which the quote is taken, Whitehead goes on (in the next paragraph) to
say

Thus
religion is solitariness; and if you are never solitary, you are never religious.
Collective enthusiasms, revivals, institutions, churches, rituals, bibles, codes of
behaviour, are the trappings of religion, its passing
forms.

To Whitehead, people
had gotten too caught up in what he calls the "passing forms" or the "trappings" of
religion.  They came to think that true religion consisted of their rituals and their
bibles.  To Whitehead, this was a problem because the trappings of religion tended to
come in conflict with science and he thought that the two of them needed to be fused,
that the conflict had to end.

So Whitehead is saying, in
this quote, that religion is not in the rituals and bibles.  He says, instead, that
religion is a personal thing that consists of what you do when you are
alone.