For what it's worth, I'm also on the determinist end of the spectrum, with a strong dose of "don't know" on the side. Our mind is basically designed to trick us into thinking we are freer than we are, while it's strongly predisposed to certain choices based on circumstances.
For instance, when something frightens you, you may remember it as: "I saw a ghost, it was scary, so I screamed and my heart started pounding". But the chronology really was: see ghost, heart starts pounding before your brain even receives the signal, get scared and scream. Your perception of it is starkly different than the reality, and your mind is reacting as much to your own physical reaction as to the external stimulus.
I'm pretty sure that there's no consensus on determinism vs free will vs "we don't / can't know for sure" among scientists, so I don't think Sheldor's claiming they're all wrong and he's right.
Thanks for backing me up. I would like to note that freewill is not the same thing as randomness, freewill is the concept of beings consciously controlling their own fate (which doesn't necessarily contradict determinism), whereas randomness (at least how I am defining it) is the concept of elements in a system giving different outputs despite having exactly the same inputs (which does contradict determinism).
Whoever is watching behaves predictably, but whoever is being watched does not.
But if free will is part of the system and not external, and free will is free and not only a consequence of external inputs, then the system as a whole will exhibit different outputs to the same inputs.
inputs -> system(laws of physics + free will) -> different outputs to the same inputs, but different choices driven by free will
Deterministic systems behave like non-deterministic ones in the presence of free will. You can even strip out the inputs for a contained system, and the system will still give different outputs.