The argument against determinism

Hello Rabbi,
In the book The Science of Freedom, you wrote that determinism cuts off the branch on which it sits: if there is deterministic causality for our cognition as well, then it does not necessarily reflect the truth, and thus this conclusion itself is not necessarily true.
And I didn't understand: Even according to the libertarian method, how come the conclusions of reason reflect the true reality? But, a rational discussion deals with what is within the limits of reason, and not what is beyond it. So also with regard to determinism, it doesn't matter what the "correct" reality is, in a discussion conducted through reason, only what reason forces is relevant, and as long as reason deduces the deterministic position, there will be no problem with that (I will emphasize that despite the somewhat decisive tone in the last lines, I am writing them only as a question)
I would appreciate the Rabbi's response.
With thanks