I wanted to respond to the suggestion in your question that if a term is vague it is thereby "pointless" -- that doesn't seem right to me. For example, although the term "bald" is vague -- we can't specify the precise number of hairs a person must have (or not have) to count as bald -- the term is by no means pointless. Perhaps there are some borderline cases where we don't know whether to call someone bald or not (Jason Alexander? Bald? Or just balding?). But that doesn't mean that there aren't plenty of clear cases: Howie Mandel, bald; Suri Cruise, not. [Aside: see here if you're concerned about bald babies.] And so the term "bald" is perfectly useful in everyday speech. [Another aside: interestingly, Wikipedia lists Jason Alexander among their famous bald people , but I'd call him a borderline case. The entire list seems suspect to me, anyhow -- why is Matthew McConaughey on the list? But philosophers are well-represented: Foucault, Whitehead, and Wollheim all make the list.] ...

Many statements that have the apparent form of a question do not function as interrogative speech acts. For example, in many contexts, if I say, "Can you please close the door?," my remark really functions as a command rather than as a question. (Likewise, my declarative statement, "You haven't closed the door" can function as a command in certain contexts.) So, if you really aren't looking for answers or information from your students, perhaps your remarks in class that have the apparent form of questions function in some other way. Perahps as commands -- when you say, "Can anyone think of a reason that ... ?" you might be instructing them to think about the issue. Or perhaps as declarative statements -- you might simply be imparting information to them. But, given what you said above, it's not clear to me that your apparent questions don't really function as questions. The fact that your students are free not to answer, and that you don't blame them for not answering, does not mean...

In addition to the points that Richard makes above, we might consider the fact that the expression "time" functions oddly in lots of constructions. Having too much time on your hands is quite different from having too much lotion on your hands, having time on your side is different from having Jack your side, and time's running out is different from Jill's running out. It might also be useful to remember that we should always be careful not to put too much weight on the surface grammar of our language. Lewis Carroll got a lot of mileage out of this, e.g., in Through the Looking Glass : "I see nobody on the road," said Alice. "I only wish I had such eyes," the King remarked in a fretful tone. "To be able to see Nobody! And at that distance too! Why, it's as much as I can do to see real people, by this light."

It sounds to me as if you've answered (at least part of) your own question -- if you don't know what you're talking about when you read the speech aloud, then how could you be said to understand it? Suppose you're a native English speaker and you don't know any other languages. A French speaker could write out, perhaps phonetically, a sentence in French and you could practice reading that sentence aloud until you could read that sentence flawlessly, but that won't make you understand it. Whatever understanding is, you would lack it. Perhaps in the case where you read the speech about nuclear physics aloud, there are many words that you understand, and perhaps even whole sentences. But for any part of the speech that you are functioning essentially as a parrot -- where you voice something without knowing what it is you're talking about -- you lack understanding.

One way to put the questions is in terms of intention -- what role does the intention of the speaker play in establishing the meaning of the speaker's words. At one extreme is the position Humpty Dumpty stakes out in the works of Lewis Carroll In a conversation with Alice, Humpty Dumpty says "there''s glory for you" and when Alice expresses puzzlement, he explains that by "glory" he means "a nice knockdown argument." On Humpty Dumpty's theory of meaning, the intention of the speaker seems to be all that matters for meaning. In response to this, there's a strong temptation to say: but "glory" does not mean "a nice knockdown argument"! So at the other extreme, someone might argue that speaker's intentions don't matter at all for meaning -- words have meaning independent of any individual speaker's intentions, and the speaker locks on to that meaning when making an utterance. You might think that the right answer lies somewhere inbetween these two extremes. A lot of philosophical work is...

My colleague Carrie Figdor, who turned to philosophy after a successful career for many years as a journalist, has this to say in response: "It’s probably too simple to think of balance in terms of a ratio; it doesn’t require us, for example, to give voice at all, let alone equal time, to Holocaust deniers in a report on World War II genocide. To paraphrase Paul Krugman: given what we know, would that even have been ethical? (See his May 2002 response to critics, On Being Partisan, here ). Being balanced is just one aspect of a complex professional norm of being objective, which also includes, at least, using neutral language, presenting views fairly, being non-partisan and just presenting facts, without inserting commentary. (For example, what do you call the structure going up roughly between Israel and the West Bank? The Israelis like the friendly “fence”, the Palestinians like the sinister “wall”; many media have settled on “barrier”. It’s still an open question as to what...

You might look at the essay on "Humour" by J. Levinson in the Routledge Encylcopedia of Philosophy . If you are at a college or university that has a subscription to this encylopedia, you can access the article online at http://www.rep.routledge.com/article/M027?ssid=391653917&n=7 #

One point that's implicit in Professor Pogge's answer above, but that it might be useful to make explicit, is that philosophers often use the notion of "person" in such a way that it contrasts with the genetic notion of "human". Whether or not you are human is a matter of your DNA. But whether or not you are a person cannot be settled by genetic testing. Rather, as Professor Pogge notes, it is usually taken to be a matter of having certain capacities. Thus, there may well be humans who are non-persons (for example, some philosophers have suggested that humans in persistent vegetative states fall into this category -- another controversial example concerns fetuses) and there may be persons who are non-humans (some advanced mammals, for example -- or if you want to get into the realm of science fiction, Data or Spock from Star Trek). Specifying which capacities are necessary and/or sufficient for personhood turns out to be quite difficult. Some of the essays in Matters of Life and Death ...

An example might help you understand the difference. Being at least 35 years old is a necessary condition for being President of the United States. You cannot be President unless you are at least 35 years old. But being at least 35 years old is not a sufficient condition for being President, i.e., to be President, it is not enough that you be at least 35 years old. Otherwise, I would be President.

There is a little book by John Perry called A Dialogue on Personal Identity and Immortality that contains a good introduction to many of the issues about personal identity over time that are raised by your question.