What is so dubious about “I”, and how exactly do you suppose its being “smuggled” in anywhere?
It may not be necessary to have a belief in the self in order to make sense of the world, but I’m not sure what that would be like. We all have a sense of self, whether its necessary for us to make sense of the world. There isn’t really any escape from this, so I’m not sure how we could understand what it would be like to make sense of the world without having an idea of self.
The sense of self is not derived from a process of abstraction, it is a direct and manifest experience of one’s own mind. We don’t get out idea of minds from looking at other people and inventing the mind as a way of explaining their behavior. We get the idea of minds from having a direct experience of one.
If “I” is mere thinking, why not just reduce it to “thinking…”, instead of something performing an act. He fell pray to the subject-object construction demanded in grammar.
The “I” is a mental substance, and possibly a soul, and its activity is thought. There is no need to eliminate the word “I” - it doesn’t add anything, or make anything more clear or understandable. In fact, for most people if you put the two sentences in front of them: “I think, therefore I am” and “There is thinking” - they wouldn’t consider those two sentences to carry the same semantic content. The subject-object construction is not a predator that Descartes fell prey to - the way we use language is an expression of how we understand ourselves and the world we live in. We use the subject-object construct because it expresses something about the human condition.
Of course I have a sense of self as well. It is a matter of belief whether there is an actual self ultimately to be found or not. I am not aware though of anyone who has made any good case for the existence of a self as defined in Buddhism - “Atman is an essence of things that does not depend on others; it is an intrinsic nature. The non-existence of that is selflessness” (Candrakirti). The notion of a self or essence can be extended to outer phenomena as well. Do ‘partless particles’ exist as was posited by some early schools of Buddhism? I’m not sure what science holds to be true at this point in history, but not that long ago ‘atoms’ held the same meaning as ‘partless particles’. If this narrow belief regarding reality were held to be true without question, science wouldn’t have progressed. So although we aren’t enlightened we can still see how belief in essences as a final truth in fact limits our ability to inquire into the nature of reality. Seeing ourselves as independent and separate substances is not a belief that we either hold in entirety or not hold in entirety. We see the world in a variety of ways that is always somewhere between those poles. Fixations and preconceptions are not encouraged in science because they ultimately inhibit scientific enquiry, even if our limited conceptions of reality are involved in propelling us to look more closely at it.
My main point here is that noone has a 100% belief in a self as defined above. We actually do make sense of the world without that 100% belief. In some Buddhist schools our lack of ability to fully understand reality is described as two ‘veils’ - the veil of the conflicting emotions and the veil of knowledge. ‘Veil’ is an appropriate word because we can and do experience and understand reality, but we are somewhat hindered. I think scientists think the same way and that most would readily agree, but not necessarily with the views and particular conceptions which are so explicitly set forth in Buddhism.
I agree that the sense of self is derived from experience. I think that saying that experience is a ‘direct’ one is debatable however. I personally believe that a ‘direct’, unmediated experience of reality is extremely rare.
It is extremely rare! It obtains in only one circumstance - our experience of the contents of our own minds.
Its not merely a matter of belief if the self is actual - we experience the self directly and constantly; we are that self. The self is not a rumor that is to be investigated. It is fully manifest and apparent. I cannot prove to you that my self actually exists, but you are entirely familiar with your self. You cannot prove that my mind exists, but it is practical enough for you to assume that I am like you. Our connectivity may be significant enough to make the problem of proof in this situation appear rather silly.
I assume the contents of your mind are as varied and confused as mine are more or less? Is it one particular content of the mind that is the self? The sum total? But if it is the sum total then that self is constructed out of parts. Since we are talking about mind (which we experience as insubstantial) maybe we should refer to ‘thoughts’ as opposed to ‘parts’? What about emotions? Or is awareness the self, independent of thoughts and emotions? But does my awareness really not depend on anything outside of awareness for it’s existence? Can there really be simply nothing at all, except that awareness is present? Or perhaps the self is somehow ‘behind’ awareness? If the self is a ‘subject’ it needs an ‘object’. Is the object unchanging and always present with the subject?
I highly prize awareness, as do most Buddhists I suspect. In fact highly advanced meditators have historically placed a very high emphasis on awareness. My sense of self comes about in the same way yours does so we have complete common ground in that respect. But I have very good reasons to trust the teachings I have been given - not least of which is that utilizing the tools of meditation I have systematically undertaken an experiential and logical search for an ‘essence that does not depend on others’ and have not discovered one yet. If I ever do and we are still posting on this site I will let you know. 
Perhaps I’ve misunderstood what you mean by self. These explorations are relevant to the Buddhist definition of self (Atman) that I gave in my previous post. Also, I don’t want to appear to disagree with the pleasure you are exuding regarding ‘directly’ (although technically I think it is veiled) experiencing the contents of our own minds. I agree wholeheartedly!
I agree except that the ‘self’ is a conception utilized to describe a reality that transcends that conception. It is an idea of singularity imposed upon a reality that is varied and continuously changing.
I would agree that our ‘connectivity’ might make the fine distinction appear silly except that I am not only discussing a philosophical position. Our belief in a self is a condition of our minds that is said to give rise to all the overt problems we see in life every day. If you ‘insult’ me and I am offended and get angry, why did it happen? It is because I ‘believe’ in the very depths of my being that ‘I’ am my ‘self’. It also follows from having a palpable sense of self that I believe my self to be better than your self. I protect the self, even viciously. And yet if my self is permanent and unchanging, why do I defend it when I believe it is being attacked?
If one ever crosses that threshold ; one won’t be able to discribe it.