...was the verbal shout from across the room/desk. My colleague's vision on determinists. Are they hippies?
Maybe its because there is an x in his last name, I don't know. But he has a point.
Determinists are people that believe that the universe is governed by solid, deterministic laws. If you say you have free speech, they say it is only input-based output of the brain. Everything is a reaction to a cause. As the famous physicist Albert Einstein (No physics blog can do without him) said: "God doesn't play dice". He meant that there is no stochastic, chance-based effects in the world. The Universe is deterministic.
However quantum mechanical observations disapprove this. In the quantum mechanics field, non-deterministic phenomenon are observed on a daily basis. Take for example the Heisenberg principle. If you know the location of the particle, you don't know its speed (exactly it is momentum, but that is the same as velocity times mass, so we don't have to bother about the weight of the statement). My dad once tried to use this principle when he got pulled over for speeding: "But officer, if you know I was driving on this highway, how did you know my velocity?" Of course, this only works in micro-space, so the assumption of my dad was wrong and the officer question exactly this part of his argumentation with a large fine.
But there are real scientific observations of this principle. Just Google Heisenberg principle experimental observations and indulge yourself in the quantum mechanics.
So where do the hippies come in the picture. To be a determinist you have to follow your gut and believe that in the end with infinite knowledge (a very accurate initial state), the universe can be propagated in the exact way. There is however no experiment to test this hypothesis. You should build two exact universes, let them progress in time and space and see if the follow the same path. This is not possible and thus there remains room for intuition and believe. A determinists believes there is no coincidence and disregards any observation that has non-deterministic phenomenon just by stating a lack of knowledge. They follow their intuition, like hippies.