On naturalism and consciousness

[Mudhammam]

To me, reason is just an instrument we have to make sense of an otherwise arational universe. It's us who give meaning to the world and find patterns in its chaos.
I really don't see why there should be a reason above and beyond the physical realm. All we know is that the (material) universe exists and it can be explained through reason.

Reason is surely inside our heads; we can't be sure it exists outside of them though.

Doesn't that render everything, even science, subjective as mere consensus opinion?