First, how exactly are you defining "traditional Christianity"? Do you mean Christianity as it was originally practiced, say, when it was a young religion in the later days of the Roman Empire, or do you mean the type of Christianity practiced by most Christians? — czahar

By traditional Christianity I mean a system of beliefs accepted by virtually all Christians at all times throughout Christian history. These are tenants of Christianity, expressed well (although often confusingly and open to interpretation) in the early church creeds.

So how would I know he'd be me? — czahar

One way to go about it is because this is what the Christian church has deemed to be a revealed truth. Acceptance of the notion that there are revealed truths is at the core of Christianity. The difficulty here, however, can arise if this kind of preservation of identity turns out to be impossible (or even highly improbably, all things being equal). In this case, we will have good grounds to say that Christianity has been wrong here. My training does not allow me to give a satisfactory answer on whether this preservation is probable or not (see Trenton Merricks and Hud Hudson, they have done some work on the metaphysical plausibility of this type of preservation of identity).

What suggests that this kind of preservation is plausible, though, is situations where, say, people born deaf start hearing. Someone born deaf has no understanding of what it means to hear. But when they hear for the first time, they discover a completely new aspect of this life. I think we can agree that they remain the same person (in a loose sense) as they had been prior to starting to hear. You may point out (and rightly so) that even while being deaf, they would likely still want to hear, because people around them seem to enjoy hearing. But suppose there is a world where everyone has always been deaf. Their religion teaches that one day they will be able to hear, but they can hardly comprehend what it means. One day something happens, and everyone starts hearing. Here, again, they likely remain themselves in spite of this radical change. Something similar applies to life without sin or imperfection.

First, there is the LDR. I tend to lose interest in activities after I do them long enough. For instance, I am an avid reader, but no matter how much I love a book, I usually have to put it down after an hour or two. Reading it for three or four hours would be painful, and reading it for an eternity would be Hell.

You might respond by telling me that in Heaven, I won’t do one activity for an eternity; I’ll do many. — czahar

I don't think traditional Christianity suggests that heaven is desirable because you do many things that you like. One of the centrepieces of Christian understanding of the afterlife (which is not identical to heaven) is an eternal worship of God. Supposedly, you will want to have everlasting afterlife for at least two reasons: (1) you will continuously grow in knowledge of God and (2) you will want to worship God.

The two are interrelated, but the idea is that in the afterlife you will be different from what you are now. Just from this point, we can already suppose that in our fallen state (again, traditional Christianity places significant emphasis on human sinfulness) we have neither moral nor epistemic grounds to properly understand the kind of wants we will have in the afterlife. In other words, on the Christian worldview, our present nature limits our capacity to even conceive of the "heavenly" ourselves. Hence, our reasons for desiring afterlife cannot be grounded in our analyses of human nature and the world the way we know them. Instead, the reasoning is something like:

1. God's revealed truths collectively indicate that afterlife is desirable.
2. God never lies.
3. Therefore, afterlife is desirable.

It seems to make sense, because afterlife is plausibly unlike anything to which we have a real-life referent. Thus, we likely have little grounds to suppose that the world we know can give us a good enough idea for construing what afterlife would be like. I still think though that there are helpful ways to think about why we would want this afterlife.

Traditional Christianity conceives of afterlife as of a state in which people will have a clearer understanding of God and of his glory. Glory/greatness deserves worship, and infinite glory/greatness deserves infinite worship (there's no need to read "infinite" in a strict philosophical sense). If we understand God to have infinite glory/greatness, we will want to offer him infinite worship. Why don't we do it now? Arguably, because we have no direct access to either God or to understanding the extent of his glory/greatness. So heaven is desirable because we will want to worship God for eternity.

Another point that can be made is something like this:

1. Knowledge of God is never complete.
2. Knowing God is satisfying.
2. The process of acquiring knowledge of God is gradual.
3. Therefore, the process of acquiring knowledge of God can last for eternity and is satisfying.

The idea here is that the more you know God, the more you love God and the more you are satisfied. Say we suppose that humans can never fully know God. Also suppose that in the afterlife we will gradually grow in our knowledge of God. In this case, we will have an everlasting source of satisfaction via gradual growth in knowledge of God that never ends.

Then what is the method of distinguishing between good and bad stuff in philosophy? It cannot be based on only preference (viz. my inclination to favour some things over others), can it?

What is then the point of doing philosophy? I understand your view to view evaluation of viewpoints as analogous to evaluation of art in that there's really no quest for either truth or arriving at reasonable beliefs.

There's some good and bad (and everything in between) in all eras. — Terrapin Station

What helps to determine what's good and what's bad?

What I wanted to show is that moral claims of adults addressed to other adults are actually the expression of personal desires in the disguise of superhuman commands (categorical imperatives). — Kai Rodewald

If God exists (and is moral), then these expressions of personal desires have a potential to get at the 'absolute' (viz. divine) morality. These claims may well be expressions of personal desires disguised as superhuman comments, but they are such and nothing more iff they are never in fact superhuman commands.

This may well be true, but I better first understand what and why someone is saying, and only then deem it as crap (not saying you don't, just stating a principle). These issues are pretty complex, and I cannot justify calling something crap without having taken a lot of time to interact with the strongest arguments for that view. Sure enough, I cannot do this for every existing thinker or system of thought, but then I should always be willing to admit, "I haven't really done my homework, so my opinion about this issue is largely uninformed." If not, I am buying into an illusion that today we have a superior worldview/values/metaphysics/morals than the people before us did. In some ways we do have a more extensive knowledge of the world, but it is fallacious to think that we are know better than they did in every way.

They might, but it needs to be demonstrated. And it would need to be demonstrated on a case-to-case basis, not once-for-all. Doing otherwise is pretty ignorant of many complexities involved in historical study of any thought ever.

I agree, every fallible human is fallible. Aquinas is not right because he's well-recognized. What I do advocate is an exercise of wisdom when it comes to evaluating positions of influential thinkers. It's something like this:

1. Influential thinkers are likely to have thought through their stuff pretty well.
2. Aquinas was an influential thinker.
3. Hence, he is likely to have thought through his stuff pretty well.

All this is to discourage people from fighting a straw man. It is way too common for people to assume that every pre-Enlightenment thinker is in some way less likely to produce convincing arguments than post-Enlightenment thinkers.

According to someone, any arbitrary thing you'd like to believe. — Terrapin Station

You're right in that Aquinas is not an arbiter of truth, but he is widely considered one of the greatest theologians of the Western church. Most likely, he had good reasons to think what he thought. It would be intellectually dishonest to liken Aquinas to anyone without first considering his arguments.

Also, under these same lines, how could Christ have been in Hell if he was a perfect, all-good God? — SapereAude

Could you clarify what exactly creates the difficulty for a perfect, all-good God to have been in hell?

I will try to work out some plausible ways to address this question though from what I understand of the apparent problem. Of course, it is problematic to find a method to arrive at any conclusion about what is 'really true' without committing ourselves to any theological framework. Many streams of Christian faith reject the notion that Christ descended into hell. Many reject the ontological notion of hell as such. But suppose we take as a given that Christ has been to hell. Here we need to note several things:

1. Unless the conception of hell in view necessarily involves that whoever is present there suffers, there is no need to think of hell in such mechanistic terms. We can plausibly conceive of hell as a place where unforgiven sinners suffer punishment for their sin. Christ is not a sinner, and hence Christ does not suffer punishment for his sins.

Now, if we do posit that Christ suffered in hell (and hell is defined as a place where unforgiven sinners suffer), there are still satisfactory ways to account for his suffering in legal terms. If we take as a given that in some sense Christ "took on himself the sin of the world," his suffering is justified. Voluntary suffering of someone else's punishment seems just in at least some context, especially if we think of justice in utilitarian terms. If the suffering of Christ brings about maximal good for the maximal number of people, the concept of his suffering in hell is both morally acceptable and coherent (at least given our commitments so far).

2. The notion of "Christ has been in hell" needs some refinement too. What do we mean by "has been?" If we speak of presence, then what kind of presence? If Christ is God, and God is omnipresent, then in some sense Christ is clearly present in hell at all times. Medieval theologians differ on how they conceive of omnipresence, but they offer some accounts of of omnipresence that render God's presence through the faculties of power (Aquinas) or knowledge (Anselm).

I hope it makes some sense. It would help to have a clearer grasp of the question and of the assumptions we are working with.