Scientific theories are explanatory models that posit ways to predict cause and effect. There are many invisible causes that have visible effects. Gravity, non-visible light, magnetism, atoms - many things that we can't see, yet they still have real effects in the world. Just because you can't see something doesn't mean you can't scientifically test it and falsify it. That is absurd.
For the spirit, you need to build your model (definition) for what the spirit is (in terms of what it does). Obviously, we know that spirits are supposed to be the invisible things that cause (effect) our behavior. Hence, according to the definition of spirit, we should be able to see its effects within bodies, even if we can't see the spirit itself. Then we scan bodies and look for the effects of spirits within them. Obviously, when we do brain scans, we don't find spirits puppeteering brains by injecting energy from an invisible dimension (violating the law of conservation of energy), and controlling decision pathways in a top-down invisible fashion. Instead, we find bottom-up processes whereby lower-level activations cause higher level activations that cycle back down to lower-level activations, such that there is absolutely no need for the spirit hypothesis in order to explain behavior.
The spirit hypothesis demands that we find injections of energy into the brain from an unknown dimension every time a decision is made. When we test this hypothesis, it is falsified every time. By this, we can rule out the spirit hypothesis and come to the scientific conclusion that spirits do not exist. There are no neuroscientists who support this model of spirit existing. The idea that science is compatible with the existence of spirits is laughable.
What caused the hand to move? The muscle.
What caused the muscle to move? The neuron.
What caused the neuron to move? A prior neuron.
What caused the prior neuron to move? A prior prior neuron.
What caused the prior prior neuron to move? The brain!
What caused the brain to move? Energy from the blood.
Where does the energy in the blood come from? The digestive system.
We can trace all of the movements in biology and NEVER is it EVER explained by the supernatural. There is no spirit that is activating neurons to move arms. There is biology activating neurons to move arms. We KNOW this because we can SEE energy in the brain. We know where the energy comes from. The energy does NOT come from an invisible source (i.e. spirit).
1. Spirit interacts with matter.
2. We can scientifically test matter.
3. We can indirectly infer things about spirits by virtue of testing the matter they should be interacting with.