Examining the fundamental issue inherent in all claims of determinism.
Daphne tells her friends that there is no free will, and everything we think and do is determined by the structure and chemical content of our brains.
“Even the sense of self is an illusion determined by brain activity,” she tells her companions.
So if all of Daphne’s thoughts and actions, and even her identity, are determined by a lump of metabolizing meat which is lodged inside the skull cabinet — then it follows that her belief that determinism is true is also just a product of her brain activity.
Therefore she cannot claim that her assertion arises from her own independent logic and reasoning.
Claims of determinism undermine the agency of the claimant. You cannot be a rational individual coming to conclusions through your own rationale if the claim of determinism were true.
In and of itself this does not mean that determinism is false, only that claims of it are irrational and self-refuting. Since we cannot know any higher truth, it is reasonable that we examine the consistency of our claims as the fundamental basis of our logic.
In this sense the entirety of the modernist/realist belief system fails, as it relies on fallacious claims, predominately determinism.