To what degree do humans have an ethical responsibility to sustain the species? Let's imagine a situation in which every single person on the planet decided to opt for voluntary sterilization (or every person of child-bearing age). Would this be unethical? Does the human species, as a species, have a responsibility to reproduce itself? Clearly, the planet and the other species on it would, on balance, be much better off without humans on it.

This is a fascinating question, in some ways, I think, it's connected to the question of whether we have responsibilities to things bigger than us in the sense of things that can continue to exist without us--e.g. things like families, nations, political and artistic movements, cultures, universities, businesses. Generally, I would say there is a moral obligation to sustain good things generally--at least where sustaining some good thing doesn't require undermining another of greater value. To your specific question: I would say that considering the species itself, there is no obligation to sustain it, since the simple existence of the species is neither good nor bad, so long as there are other species to substitute for it. Considering the species as part of the larger ecosystems of the planet, where genetic diversity is salutary for the health of living things generally, there is an obligation insofar as the well being of living things is good. Considering the existence of the species as the...

Why is it that solipsism can't be 100% refuted? It seems that the theory is very flawed and is called incoherent. And if this is the case then why is it said to be irrefutable? Is the only reason that it can't be refuted is because we can't directly experience what another peron is experiencing, so in other words we can only experience life through ourselves. Is this correct?

Hume once described skepticism as a "malady that can't be cur'd" (a colleague of mine says it's like herpes in that way), and perhaps it's the same with solipsism. The suspicion that it can't be fully refuted depends upon the concern that any reasons brought against it might be gounded simply in the contents of one's self or one's own mind--and that one doesn't fully know oneself or one's own mind. So, pehaps the world and the people in it one experiences are something like dreams or hallucinations. Perhaps the ideas and languages one encounters are one's own invention. Perhaps one's mind has the power (and exercises the power) to create or imagine everything we experience and think and feel, but that power remains hidden from consiousness. One of the most persuasive strategies for subverting solipsism in recent years has been to show that the very thoughts and language in which it is expressed require others to make those thoughts and words meaningful. So, the very existence of the thought and...

Is there any way for consciousness to be measured? What does it mean to say that my consciousness is at a higher level than that of my dog, or that my dog is at a higher level of consciousness than a flea, or that the flea is at a higher level of consciousness than a rosebush? What are we measuring?

"Higher" and "lower" can be quite slippery terms, and your not likely to find philosophers using them in serious contexts. But one might say that different forms of consciousness can be distinguished by the different capacities they possess and the relative detail, discrimination, or complexity of those capacities. So, a form of consciousness that were capable of 600 shades of emotion might be described as more complex than one with only 2. A form of consiousness that possessed self-consciousness, a distinction between self and world, a capacity for memory, for imagination, for planning, for deception, for long attention spans, for causal reasoning, for symbolic thought, for invention, for metaphor, for memory, for mathematical reasonsing, for logical reasoning, for abstraction, for language acquisition, for a vocabulary of the size of the English language, for spatial conceptualization, for music, etc. might be thought of as "higher" than forms of consciousness without any of these capacities. ...

Do you think that there are important differences between general thoughts (like "People are animals" or "Everybody must pay their taxes") and concrete ones (like "That cat is an animal" or "I must pay my taxes")?

Well, there's "important" and there's "important," but I'd say that the most important difference is in the sorts of logical things one can do with each kind of thought. There are many different forms of argument that depend upon what logicians call fully "distributing" their terms. So, from "All people are animals" we can reason quite easily to Anna Nicole was an animal. But from the fact that "That cat is a pet that belonged to Anna Nicole" we can't reason to the idea that "All cats were pets that belonged to Anna Nicole." In fact, you might say that to a large extent, the sciences are concerned with general ideas, rather than concrete ideas, as you describe them. There are, of course, poetic differences, too, that might sometimes be important. Perhaps the most important thing about concrete ideas is that they refer to the existential particularities of one's own life in a way that general ideas don't. Or perhap better, general thoughts are important to one individually only to the extent that...

Is the sale of human organs ethical?

It is difficult to give an answer that would cover all possible cases, and I suppose I can imagine an individual case where purchasing a organ would be permissible. But as a practice or policy, it is not ethically permissible--this because a market for organs would provide incentives for people to sell when they shouldn't--for health reasons and otherwise. The poor and desparate would be exploited in the most horrific ways. If you'd like an example, the film, Dirty Pretty Things , offers a compelling portrait of just the sort of exploitation a market in organs would cultivate.

Does music have any intellectual content?

As opposed, I suppose you mean, to affective or emotional content? Yes, both in the lyrics or librettos of various musical compositions and in the web work of meanings that have come to be attached to various sounds. Like most, if not all, artforms, music exists in an historical context, and within any context music relates to other music. So rhythms, harmonies, instrumentation, chord progressions, intonation, etc. evoke symbols, social ideas, abstract ideas concerning music theory, social criticism, human relationships, the divine, etc. Musical compositions themselves are associated with cultural movements (modernism, tradition, militancy, rebellion), fashion, politics, even entire civilizations (the Europe, Africa, India). When we listen to a song, we listen to a history and to a society.

I've been reading lots of papers recently based around 'the Argument from Evil', its replies, the theodices and their objections. I'm agnostic but have always thought that the best reason for why non-human animals and children suffer in such terrible ways is because if they didn't we wouldn't question the existence of God. If we didn't have arguments based around a young fawn dying a slow, agonizing death in the forest then the Argument from Evil wouldn't be as effective as it is. We could come up with answers based on redemption from sin and so forth. The same can be said for AIDS, the plague, Auschwitz, whatever. The notion of mystery on the issue and freedom of thought that goes with it is in my mind one of our greatest gifts. If we didn't have these terrors then a beautiful sunset or a kind gesture or the stars would be enough to convince most of us (or at least a fair few of us) that there must be some kind of God. This doesn't seem to be covered by any of the theodices; the closest I can...

The problem of theodicy is a marvelous one, isn't it. I can't tell you how much pleasure I've culled from it, as have my students. For myself, I can't think of anyone whose put your point in exactly this way--but I don't pretend to command the enormous literature on the subject. I think an objection, or at least a question, might be raised to your point along these lines: Why is it better that people question the existence of God than not question? Wouldn't it be better if God were simply manifest to all and that there were no good reason for doubting God's existence? What possible advantage is served by God's hiddenness that isn't overwhelmmed by the enormous loss of souls it yields? You yourself raise a second objection: there seems to be a superfluity or excess of evil even if your point is granted. Therefore, the idea that evil is justified because it makes it possible to question God's existence doesn't seem sufficient.

Did teleological arguments give us reasonable grounds to believe in a Creator before Darwin?

The issue of what's to count as 'reaonsable' is a fascinating one, indeed. Part of the answer depends upon whether what one thinks is reasonable is in some sense transhistorical or whether it changes over time as people develop different norms of rationality. There's a larger than many realize contingent number of philosophers even today who think telelogical arguments reasonable. But your question is about how things stood before Darwin. In my own view, whether you think norms or rationality transhistorical or not, David Hume's argument's against the teleological argument in Dialogues concerning Natural Religion (1779; first composed in the 1750s) were decisive nearly a century before Darwin. Since, Hume I don't think one really can regard the telelogical argument as reasonable.

Have the advances in brain scanning techniques that allow the brain to be monitored in real-time had an effect on the philosophical discussions regarding the mind/body question? If so what are they? I'd be interested to find out what a student of Wittgenstein or Peter Winch had to say about the subject?

Wittgenstein once posed the following question: If one could open up the top of one's head and then hold a mirror in front of oneself so that one could see inside one's own brain, would one see one's thoughts and feelings? It seems to me that the answer is no, and so whatever the relationship of mind is to body, brain activity is not properly called thought and feeling. Realtime monitoring of the brain gives us something like Wittgenstein's mirror. It shows us what goes on in the brain when we think and feel. But it doesn't follow that we should call what it shows us thought and feeling.

If science is based on observable, measurable data, what is the basis of science's belief of the origins of the 'Big Bang'? Even religions talk of the cataclysmic beginnings of the Universe, but they don't claim the Bang was of Nothing. Observable, mathematical data suggests nothing begets nothing.

This gets a bit beyond my expertise, but I suppose like you I find these sorts of issues irresistible. (Kant thought that part of that irresistibility was a feature of our being rational beings, by the way. Perhaps he was right.) Anyway, I'm not exactly sure what you mean by "origins of the 'Big Bang'," but I'm unaware of any scientific theories advance any position at all on any cause or originary reason for the big bang. The bang itself, perhaps from an original singularity, is as far back as natural science goes. Indeed, in a sense, it makes no sense to speak about any time before the big bang, since as I understand it time began with the big bang, too. Now, I have encountered speculation about the big bang being one in a 'series' of big bangs--where a bang would be followed by a period of expansion, which would be followed by a contraction back to a singularity, which would be followed by another big bang. But that still wouldn't offer an explanation about why this cycle exists in the...