We might wonder whether world peace would be so desirable. Isn't some conflict rather stimulating and exciting, and would it not be boring if everyone was in perfect harmony with everyone else? Of course, peace would be preferable to immense murder and destruction, however lacklustre it might turn out to be. On the other hand, an ideal state of affairs might be thought to include at least some conflict and aggression, and so the ideal of world peace may not be realized because few people actually want it to be realized.

Exactly the difficult with the "life is sacred" slogan. If a choice has to be made between lives, how does one carry it out unless there is some way of balancing lives against each other? On the other hand, one can see the logic of leaving it to God, if one believes in him, since how can we play one life against another? As the Talmud puts it when considering whether one person should be sacrificed for someone else, how do we know whose blood is redder? I think that means it is not possible to say that one person's life is more significant than someone else's. For a consequentialist, though, this just looks like a decision not to enter into a calculation at all when there are instances where this should be done. Triage is based on the idea of the efficient use of limited resources, and it seems right to treat a patient who looks as though she might recover as compared perhaps with someone who looks as though they will not. It might still be argued that life is sacred, but interpreted in such a way...

I would add to the helpful suggestions that there is nothing like working with the students on an actual extended text, like one of the shorter Plato dialogues, perhaps, or some of Russell's essays, to bring them into direct contact with a philosopher. I have often found that this is effective in instilling enthusiasm for the discipline as compared with exclusive reliance on a reader or survey.

I think the questioner is hinting at the ethical nature of killing things that can feel pain, given his examples, and he does raise the sort of issue that vegetarians and others have often found compelling. If a pig, for example, is perfectly happy nosing around in a yard are we morally permitted to kill it and eat it? Are not many animals capable of enjoying their lives, and why should we be allowed to interfere with them by killing them? This seems to me to be the challenge in the question, and it is a powerful one.

On the other hand, when it comes to romantic love there is a sense in which too much knowledge might be thought to be a distraction. For example, we often compartmentalize our relationships with people, keeping separate different aspects of their personality in our minds because we suspect that were we to confront them fully we might have to change our relationship with them. The interesting question perhaps is how much we should know about a person before we can say that we really love him or her, as compared to feel lust or friendship. And this raises another interesting question, which is how much should we know about ourselves before we can properly classify a relationship as based on love as compared with some other emotion.

Let me address your first point which reappears towards the end also. I think there are thinkers nowadays who have faith and hold that this justifies their religious beliefs, but not in the sense of establishing them logically. They would often claim that faith is a perfectly acceptable way of believing things, and provides a reason for belief, but not the sort of reason that would have to be universally accepted by anyone professing to be rational. I don't think it is just a matter of having the faith one is brought up in, people do after all convert to different religions or from no religion to a specific religion. Of course, some philosophers think that religious beliefs may be shown to rest securely on both facts and valid arguments, and for them faith is merely a different kind of justified belief. Others though think that faith is a very different kettle of fish and one that should not be dismissed just because it is different from philosophy. Philosophy does not help us work out how to play...

In fact, it is often said that the finitude of everything in the world of generation and corruption is only possible if at least one thing is infinite, since there would otherwise be an infinite regress of one thing bringing about something else.

If fish feel pain, then I cannot see how it could be easily justified. Even if they don't feel pain, fishing might mean interrupting their lives unjustifiably, if we were to keep them out of the water, although if we were to throw them back this would not be such a problem. Of course, it might be that we would need to fish to stay alive, and then a new set of considerations come in. But unless some good argument can be produced to show that fish as a life form are not deserving of consideration, I cannot see how fishing is morally acceptable.

Why shouldn't we find things in nature beautiful? I am actually very impressed with the caw of the crow, which to me is a sublime sound. There is no requirement that something be humanly constructed for it to be beautiful, many would say quite the reverse.

I suppose for an agnostic immortality just has no connection with a deity. If immortality is just the memory we leave, or the impact we have on others, then there is no need for any religious context for these ideas to make sense. I wonder though whether immortality does have any connection with the motive to be religious since so many religions seem not to have a belief in immortality, or a very indefinite belief in it.