Almost! You began with "A yellow chair isn't in the set of chairs because it's yellow [but rather because it's a chair]." So I was expecting "A beautiful painting isn't in the set of paintings because it's beautiful [but rather because it's a painting]." Your insertion of "good" spoiled the analogy.

Merriam-Webster defines the relevant senses of the verb "become" as "come into existence"; "come to be"; and "undergo change or development." Given that definition, how about this argument? (1) Necessarily, whatever comes into existence, comes to be, or undergoes (qualitative) change or development exists at the end of the process of coming into existence, coming to be, or undergoing (qualitative) change or development. (2) Necessarily, whatever exists is not nothing. (3) Therefore: It is impossible for something to become nothing. If that argument is sound, then it's only in a figurative sense (rather than a literal sense) that something becomes nothing when it goes out of existence.

I think the wording of your question contains the answer. You define an objective view as a view that is true independently of human opinions. A view can satisfy that definition even if every view is someone's view. The fact that no view can be held without being held by someone doesn't imply that no view can be true independently of human opinions. Take a simple example: If your view is that elephants are bigger than mice, your view can be true independently of human opinions even though it's held by a human and formed on the basis of human perception. It's a separate issue how you know that elephants are bigger than mice. But the objective truth of the view isn't threatened merely by its being your view.

When you say that "species...care for each other and co-operate with each other to ensure the survival of their own species," I take it you're referring not to all species (including all plants, all microbes, all invertebrates, etc.) but only to those species whose members care for each other and cooperate with each other, which may be a minority of the species that exist. Anyway, you ask whether something like the following argument is "fairly viable": 1. The members of all species [of the restricted kind referred to above] act so as to promote the survival of their own species. 2. Therefore: We humans ought to act so as to promote the survival of our own species. As you seem to recognize, the argument isn't logically valid: The premise doesn't logically imply the conclusion. But the argument can be made logically valid by inserting a premise, such as P. We humans ought to do what the members of all species [of the restricted kind referred to above] do. One problem is that P itself is highly...

As I understand it, the distinction between brute facts and other facts is that a brute fact has no explanation (not simply an explanation we fail to know) whereas any other fact has an explanation (even if we don't know the explanation). Contingent facts could have been otherwise: they could have failed to be facts. Noncontingent facts couldn't have been otherwise: they couldn't have failed to be facts. Given the history of scientific explanation, I see no reason to accept the existence of brute contingent facts. Many contingent facts that seemed to resist explanation were later explained. I see no reason to think that many of the facts that now seem to resist explanation won't themselves later be explained. One way for every contingent fact to have an explanation is for there to be an endless regress of contingent facts. I see nothing wrong with such a regress. Assuming that the existence and nature of our universe are both contingent, they would be explained by an endless regress of contingent...

I think your friend's argument by dilemma leaves out this possibility: we were made by a deity (or deities) principally in order to lead happy lives rather than principally in order to serve it (or them). Even so, our having been made for the purpose of being happy wouldn't make being happy our purpose . Instruments made for a purpose thereby acquire that purpose (although, of course, they can later be repurposed). But people aren't instruments; I doubt that they're the kind of thing that can be given a purpose, even by their maker. Or at least, because they're autonomous, people can thwart any attempt by their maker to give them a purpose. Hence I don't think there could be any such thing as "our purpose in life," if "our" refers to people in general. So I agree with your friend's conclusion (although for different reasons than your friend gave): our purpose in life can't be to be happy. Nor can it be anything else.

One of philosophy's most important uses is in helping us to spot bad questions. It's better to diagnose the defect in a bad question than to try to answer a bad question straight up. Take your question, for instance. Its defect is your false dichotomy : your assumption that any discipline either can prove or disprove things or else is inconclusive and useless. It might be neither of those. Historians of Tudor England can't prove or disprove things, if that means answering historically interesting questions with absolute certainty: their historical evidence doesn't allow them to do that. But of course that doesn't make the history of Tudor England a useless area of inquiry, and if it's not useless then it's not inconclusive and useless. Your false dichotomy aside, philosophy does prove some things, such as the principles of logical reasoning. Less abstractly, philosophy often proves that some theory consisting of specific propositions A, B, C (say) is logically committed to some other proposition...

The external-world skeptic purports to show that I can't know any external-world proposition P. How about this response? 1. Conceptual analysis reveals that knowledge is nothing more than reliably produced true belief, where reliability falls far short of logical infallibility. 2. If knowledge is nothing more than reliably produced true belief, then the skeptic's sensitivity condition on knowledge is false: I can have a reliably produced true belief that P, and hence knowledge that P, even if I would falsely believe that P if I were being deceived by an evil demon. (Analogy: My gas-engine car can be reliable even if it wouldn't work at all if it were on the airless surface of the moon.) 3. In particular, I can have a reliably produced true belief, and hence knowledge, that I'm not being deceived by an evil demon even if, were I being deceived by an evil demon, my belief that I'm not being deceived would not be reliably produced. The skeptic then predictably asks: "But how do you know...

If by "laws of thoughts" you mean laws of logic, then no. No coherent (that is, self-consistent) situation can violate any law of logic. Even philosophers, such as Graham Priest, who claim to be able to imagine situations that violate the law of non-contradiction concede that those situations are not self-consistent.

What makes a "heap" of sand is not only how many grains of sand there are, but also how those grains are arranged. If you took a "heap" of sand and stretched it out in a line, you would have the same number of grains, but it would no longer be a "heap." Agreed! Even so, there must be a sharp cutoff between (a) enough grains to make a heap of sand if they're arranged properly and (b) too few grains to make a heap of sand no matter how they're arranged. An instance of (a) would be 1 billion; an instance of (b) would be 1. Why must there be a sharp cutoff between (a) and (b)? Because otherwise (a) can be shown to apply to 1 (which clearly it doesn't) or (b) can be shown to apply to 1 billion (which clearly it doesn't). That's what the sorites argument shows. ...obviously we can have heaps of sand without knowing exactly how many grains of sand are required to distinguish a "heap" from a pile of individual sand grains, or else there would not be a so-called "paradox" in the first place! You seem...