Let us consider a deterministic universe. What is possible? What is impossible?
What is possible is that what happens, what is impossible what what doesn't? No; both words concern a freedom that is lacking in the universe. Some things occur, some do not. One can't say with certainty that an event is possible until it has occurred, and by that time it's too late, just as an act can't be considered impossible because it hasn't yet happened.
The words 'possible' and 'impossible' imply prediction, thus an element of free will. Many words have a sense of time built in: 'cause', 'effect', 'try', 'become', 'perform', etc. Words which reference our experience of time are meaningless in a deterministic universe because time in such a universe is a dimension and not experienced as the unknown, unfolding phenomenon which we experience on a daily level.
In philosophy, consider the most simple of logical propositions: 'if A then B'. This statement itself includes an element of time. Can this convey any meaning in a deterministic or fatalistic universe?
This is problematical. Perhaps language, perhaps any form of communication, are incorrect tools to describe a non-temporal universe.
Writing and language are conveyed one word at a time, temporally. Is all communication temporal? Communication is a gaining and growth of information, so yes.
Can communication, an exchange of information, occur in a completely timeless universe? No. Let us see all of time and space as one object. It may contain information but we cannot certainly state where it originated from; the word 'originated' itself implies a past, but we can state that the information exists in its location.
The most stark implication of this reasoning is that any essay on free will or determinism, is already free and non-deterministic because it is an essay, thus using language to convey information temporally, unlike the universe. Perhaps it is possible to describe a deterministic universe, but this description would necessarily be non-deterministic. This does not necessarily prove that a deterministic universe cannot exist.
It appears that there are two universes at work, both present and overlapping like transparencies:
1. Our daily, natural experience of time as a phenomenon unfolding the unknown, which we know and experience on a daily basis. As this is necessary for communication and the exchange of information, then it is not exclusive to humanity, or humans and higher animals, but for all phenomena which communicates, from planets sharing gravitational information to atoms sharing electromagnetic data. The future, in this universe, is necessarily unknown because communication of the known necessitates some quantity of the unknown.
2. An eternal and timeless universe where no communication takes place, but one where the future is known. How can it be shown that this exists?