Why must there be a “thinker”? When you feel a breeze, you don’t assume there must be a “blower”.The “I” is an invention, the main character in the story the brain concocts to account for experience.
Do “you” make your heart beat? That’s not the common way of looking at it. It feels like you are irrelevant to the process; there’s no apparent need to involve an “I’ in explaining it because it seems to happen all by itself . But the beat, of course, originates in the action of the neurons of a nervous system.
Do “you” make your respiratory system breathe? This question is harder to answer, because sometimes it seems like “I” take a breath, and sometimes it seems like “I” have nothing to do with it.
And yet we always come to the conclusion that “I” am doing the thinking even though this too is nothing but the action of neurons. The difference seems to be the feeling of will that accompanies some experiences, but not others. Some actions seem to come from a controlling “I”. But research indicates that these actions begin in the brain well before there is any awareness of making a decision. The decision is made without you. The “I”, the “thinker”, just gets pasted on later in the process.
This is all very contrary to the way experience is conceived, but that’s because the thought of “I” is fundamental to the brain’s process of building a conscious representation of a world. Data must be presented to a computer in the form of 1s and 0s even though the whole of reality can’t begin to be reduced to 1s and 0s. You could never explain to a computer that the 1s and 0s are just expedient ways of representing reality, but not reality itself. Likewise, the brain has trouble dealing with the fact that “I” is just such an expedient, without independent existence.