I think, therefore I am is what Descartes famously said. He seems to clarify later that the thinking is undeniable, but that little can yet be concluded about the nature of the thinker. A critique that you can make, and is made, is the “I” in this phrase. How could Descartes concluded thet the “I” he identifies with is the thing that does the thinking?

It is hard to ignore the feeling that there is something in us that does the thinking and that we call I. The reason is that I feel like I think about it. But the I that thinks is also the I that makes bodily sounds, and how much do you control those?

In light of this, “I” seems more like a linguistic tool we use to communicate with others and with ourselves. Our bodies breathe and digest without our intervention, yet we still say that we breathe and digest, just as we say “I think this or that,” even though our control over thinking may not be very different.

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But man’s craving for grandiosity is now suffering the third and most bitter blow from present-day psychological research which is endeavouring to prove to the “ ego ” of each one of us that he is not even master in his own house, but that he must remain content with the veriest scraps of information about what is going on unconsciously in his own mind.

Freud, Introductory Lectures on Psychoanalysis, Part III, Lecture XVIII (https://archive.org/details/in.ernet.dli.2015.278046/page/241/mode/2up)