You give an interesting argument that the ground of one's identity is biological rather than (just) physical and/or psychological. But it may run into a problem. Not only can one's body reject organs transplanted from someone else. It can also, in the case of autoimmune disease, "reject" (i.e., attack) one's own cells and tissues: sometimes the body doesn't "know its own." Yet it seems incorrect to say that sufferers of autoimmune disease have a "compromised" identity. Does this problem cast doubt on your proposal?

I'll assume, just for simplicity, that by a "thought" you mean a belief and by "something impossible" you mean a proposition that cannot possibly be true . I hope my assumptions aren't off the mark. (I'm not a neuroscientist, so I'll say nothing about how neurons work.) If my assumptions are correct, then your question becomes "How can anyone believe a proposition that cannot possibly be true?" One answer is this: "Easy! For example, many people down through the ages believed that they had accomplished the famous geometric construction known as squaring the circle . But the proposition they believed cannot possibly be true, because squaring the circle is impossible, as was finally proven in 1882. Those who believed the proposition obviously didn't see the impossibility of the construction." An opposing answer is this: "They can't! Indeed, we can understand the behavior of those misguided geometers only if we attribute to them a false belief that could have been true, such as the belief that a...

First a terminological quibble. By "scientifically impossible," I take it you really mean just "technologically infeasible," i.e., impossible given the limits of current technology. As I see it, what's scientifically possible or impossible depends only on the laws of nature, which are standardly regarded as unchanging over time (or at least over any time that humans will experience). I think the jury's still out on whether backward time-travel is scientifically impossible in this latter sense. To your question: I think there's something self-contradictory in the idea of "correcting what you did" if that means "bringing it about that you never did what you in fact did." Either (1) you did it, or (~ 1) you never did it. I can't see how any consistent story features both (1) and (~ 1). In that sense, then, there's no such thing as (2) "going back in time and changing things in reality" and therefore nothing that's "the same as" (2). See section 1.2 of the SEP article on time-travel .

For an accessible and up-to-date discussion of these issues, I recommend Time, Language, and Ontology (OUP, 2015) by Joshua Mozersky. The author's interview at 3:AM Magazine contains a good overview of the book.

I'm not sure why you regard it as a worrisome sign about current philosophy of mind that some of its practitioners take eliminative materialism (EM) seriously. At worst, it would show that some philosophers regard EM as far more plausible than it really is, but even then I don't see how that would indict current philosophy of mind as a whole. Anyway, you've asked an empirical question whose answer depends on (1) reliable data about the views of philosophers and (2) what you mean by "take seriously." I presume you mean something like "regard as too plausible to be dismissed without argument," which is a weaker attitude than "regard as plausible." I don't have empirical data, but my hunch is that most philosophers do take EM seriously in that sense, but probably because most philosophers don't regard any philosophical position as worthy of being dismissed literally without argument. At the same time, however, my hunch is that most philosophers regard EM as implausible. Curiously, the PhilPapers...

Must we accept that for all cases of mental phenomena ... the brain scan test constitutes a proof? I think the important philosophical question here is "A proof of what?" Suppose that science did somehow establish that all of our choices are causally determined by our earlier brain states. According to compatibilism , that result wouldn't threaten free will at all, and according to many compatibilists it would be good news indeed for free will. Before we get too hung up on whether brain scans are evidence in favor of determinism about human choices, let's ask the prior philosophical question "What difference would that make for free will?" You'll find this issue discussed many times on this website, including here: Question 5451 Question 5711

I'm strongly inclined to say yes . Here's an argument. If there's even one technological civilization elsewhere in our unimaginably vast universe, then that civilization must have discovered enough math to produce technology. But we have no reason at all to think that it's a human civilization, given the very different conditions in which it evolved: if it exists, it belongs to a different species from ours. So: If math depends on human consciousness, then we're the only technological civilization in the universe, which seems very unlikely to me. Here's a second argument. Before human beings came on the scene, did the earth orbit the sun in an ellipse, with the sun at one focus? Surely it did. (Indeed, there's every reason to think that the earth traced an elliptical orbit before any life at all emerged on it.) But "orbiting in an ellipse with the sun at one focus" is a precise mathematical description of the earth's behavior, a description that held true long before consciousness emerged here....

Interesting, but it's an empirical, psychological question rather than a philosophical question properly so-called. I therefore recommend asking a psychologist or looking into the psychology literature. Any philosopher who tries to answer it is doing psychology, and probably from his/her armchair.

You asked, "If the physical processes that give rise to thought are rational, how can a human being have an irrational thought?" You might be misinterpreting the claim that "the physical processes...are rational." Presumably what's meant by the claim is that the physical processes can be discovered and understood by rational means , such as empirical investigation and logical reasoning. The claim doesn't mean to attribute rationality to the physical processes themselves: the processes don't literally investigate or reason, either well or badly. So the fact that the physical processes can be discovered and understood rationally doesn't imply that irrational thoughts can't result from those processes. Furthermore, we can rationally investigate the physical causes of irrational thoughts, even if science isn't very far down that road at present. In any case, we should resist the suggestion that the universe sometimes violates the laws of logic: that suggestion is either impossible or not even...

I'm inclined to think that there are, and perhaps must be, things that humans can't understand because of the limitations of our brains. Now, the term 'understand' might mean (i) 'understand at all (i.e., at least partly)' or (ii) 'understand completely'. On interpretation (ii), it's pretty clear that there are things we can't understand, because our finite brains can't grasp all of the infinitely many facts there are about even as ordinary a thing as my car. What's my car's exact mass right now? (No rounding allowed!) Even on interpretation (i), there may be things that humans can't understand. The only organ with which we can hope to understand something is our brain. Why wouldn't our brain's finite capacity for information storage, calculation, and so on, be accompanied by a finite capacity for understanding things? Indeed, Colin McGinn has conjectured that some of the central problems of philosophy have endured for so long because, although they have solutions, our species lacks the ability...