Reason is an analogy of the concept of the ‘unmoved mover’, but with the beauty of revealing it’s not unmoved at all.
It’s just that the ‘unmoved’ and the ‘moved’ cannot coexist because they are opposites. Each is the thing that the other is not, but both can know the difference.
And so it is not true that the ‘unmoved mover’ does not exist, or indeed that it is unmoved. It is just unmoved to the degree that the moved has moved.
If we are therefore able to recognise the ‘moved’ then this demonstrates a change or divergence from the opposite equilibrium of the unmoved and the moved. Knowing then that what moved is categorically what the ‘unmoved’ is not, the ‘unmoved’ is also known.
And it’s not knowing this that is existence; it’s knowing the reason – that is existence.