Do you believe that murder is wrong? (I'm not talking about executing criminals or other questions of justice - I mean the raw "He has a shiny watch and I want it, so I'll cut his throat and take it"). And because that's such an obvious question I'll go further and ask "WHY is it wrong?"
To answer the question, I do think it is wrong. But that begs the question of what is right and wrong? Where do these ideas come from? I will note that these ideas are questions of morality. So then the question becomes, where do we get morality from. Obviously a religious person will answer they are "from god", because in their context, man is by definition evil (or at the very least "flawed"), so there for all goodness (and ability to discern goodness) comes from that absolute good they associate with god. In fact this is not too far from the track that Lewis takes, it's pretty effective, but to me it isn't a compelling case.
Here's why. In my context (skeptical), I do NOT view man as evil, or even flawed. I see man as a being of volition (free will). The fact that we are volitional means we have to choose to do good or choose to not do good. And part of being able to choose the good is actually knowing what the good is.
And this brings us to the question of "concience". Why do humans seem to know "instinctively" when they are doing something wrong, and why are they bothered by it. Since we have discounted the god explanation, we should look at nature. Here are my observations. Certain animals (including man) are "social" or herd animals. The likelihood of their survival (as a species) is higher if they stick together. 2nd observation - within a species, you see intense competition (especially for mating), between species members, but it is rare that you actually see members of these social species actually turn on each other and start killing the competition.
From that, here are my conclusions - that survival of the species supercedes survival of the individual. Millions of years of evolution have programmed this in to almost all walks of life, and it is especially strong in social species that often have better survival chances via cooperation instead of mortal conflict.
So, we are biologically programmed to value human life above all. But of course, being creatures of volition, we can choose to ignore or go against that imperative. When we do, we feel "bad", and have twangs of concience. And if you follow it out with specific examples, most things that we feel "bad" about almost always have a component of harm done to another human being.
So, to sum up, I would posit that morality is the result of our species valuing human life above all. If that is the standard, then morality not only makes sense from a social stance, but from a biological stance as well.
In fairness, you probably make one exception, because pretty much everyone does. You probably believe (becasuse our physicists tell us so) that the universe had a beginning, a time 0.
Actually, I don't. Physicists are capable of mistakes, like anyone else. I happen to think this is simply a mistake on a massive scale. It's certainly far in to the realm of "speculative" physics (ie, there's some evidence that "might" be interpreted this way, but it's far from definitive at this point). Besides, the very idea of the universe being created voilates the basic truth of physical reality that nothing is created or destroyed, it merely changes form. Toss in to that that most physicists that seriously advocate the big bang will admit that once all that mass and energy is reduced to a certain size (and therefore, density), that "the laws of physics as we know them break down". Well, once you admit that the very tools you've used to get you to this point are no longer valid, you've evicted yourself from the realm of science and landed in the realm of speculation and make believe. It's a cop-out on a massive scale.
I believe there is a fundamental mistake being made in that they are "setting out" to find the "beginning" of the universe. But what if there is no beginning. What if the Universe is simply eternal? You might say "If the universe is eternal, why is everything moving away from everything else and a constant rate, which is consistent with the big bang theory?". Good question. Here's an alternative interpretation (and believe me, it's ALL interpretation once you get past the basic data), it's that we know black holes exist on a local scale. What would happen if a looooooong time ago a "black hole" became so massive that it simply sucked in (or most) matter/energy in the universe, then when it reached a certain density level, the process voilently reversed, creating what appears to us now to be a "big bang".
Now, you can certainly say that "that's not provable, we have no idea what happened before the "big bang", and that's precisely my point. WE HAVE NO IDEA WHAT HAPPENED BEFORE THE BIG BANG. It's ALL speculation, and that's true no matter how much scientific lingo you dress it up in. So, given those criteria, my interpretation is just as valid as the standard interpretation that everything was "created" in a single instance (which is ridiculous on the face of it. Created? From what? How? No answer from the scientists, that's for sure).