Who Writes Your Thoughts?

Who writes your thoughts?
Presumably, you.
But how can you author a thought
before you have it?

To do that, you’d have to know
what you were going to think
before you thought it.
And if you knew
what you were going to think
before you thought it,
you’d have already thought it.
In that case, there would be no
before-the-thought
or after-the-thought.

But there is a before-the-thought
and an after-the-thought.
Therefore, “you”
(in the sense that we mean)
can’t have written the thought.
But if not “you”
who?