I just don’t think the question is about determinism and probability at all. When we think, our thoughts are influenced by any number of extra-logical factors, factors that operate on a level of abstraction totally alien to the logical content of thought. Things like chemical reactions in our brains or whether the sun is out or whether some sound distracts us or a smell reminds us of some memory. Whether these factors are deterministic or probabilistic is irrelevant — if anything the effect of these factors on our thinking is deterministic. What matters is that the mechanical process of producing thought is clearly influenced (perhaps entirely!) by non-rational factors. To me this means that any characterization of the essence of thinking that relies too heavily on its logical structure cannot be telling the whole story.