Mechanical Determinism

Newtonian mechanics is a complete system. Given a state of a system of particles and the mass, velocity and position of each particle, the state of the system – the position and velocity of each particle can be determined at any subsequent or previous time by application of Newton's three laws of motion and conservation of momentum to every collision.

In practice, the initial masses, positions and velocities cannot be measure with absolute certainty, so any predictions made are not completely accurate, but this does not change the philosophical point that the Universe is a deterministic machine according to Newtonian mechanics. The future of the Universe is exactly determined by it's initial conditions, and if any other Universe were to start with the same set of conditions then it would follow the same history as ours.

Newton's laws apply also to biological systems, which are made up of atoms, the atoms also being made up of electrons, neutrons and proton, the protons and neutrons made up of quarks. We can apply Newtonian mechanics on any scale to predict the future of the system.

When Newton's theories were publicised and the implications were realised, the church had a problem. Where was the need for God in a Universe governed by such precise physical laws? In fact Newton's theory is not inconsistent with the presence of a God. It could easily be the case that the Universe was set in motion by a God and left to run it's course according to Newton's laws. The Universe might be a clockwork Universe, but needed a God to wind it up.