A little self-education goes a long way. Let Richard Dawkins enlighten you (and if you’ve seen this already, it’s never a bad idea to brush up on the basics of life):
Why is it wrong to kill babies? Why is it wrong to take advantage of mentally retarded people? To lie with the intention of cheating someone? To steal, especially from poor people? Is it possible that Medieval European society was wrong to burn women suspected of witchcraft? Or did they save mankind from impending doom by doing so? Is it wrong to kick rocks when you’re in a bad mood?
Questions of right and wrong, such as these, have for millenia been answered by religious authorities who refer to the Bible for guidance. While the vast majority of people still turn to Abrahamic religious texts for moral guidance, there are some other options for developing a moral code. Bibles aside, we can use our “natural” sense of what’s right and wrong to guide our actions; a code based on the natural sense would come from empirical studies on what most people consider to be right or wrong. Ignoring the logistics of creating such as code, we should note that the rules in this code would not have any reasoning behind them other than “we should do this because this is what comes naturally.” How does that sound? Pretty stupid.
The other option is to develop a moral code based on some subjective metaphysical ideas, with a heavy backing of empirical facts. “Subjective” means these ideas won’t have an undeniability to them; they are what they are and that’s it. Take as an example the rule such as “we should not kill babies.” There is no objective, scientific reason why we shouldn’t kill babies. Wait!, you say, killing babies is wrong because it harms the proliferation of our species and inflicts pain on the mothers and the babies themselves! But why should we care about the proliferation of our species? About hurting some mother or her baby? While no one will deny that we should care about these, there is nothing scientific that will explain why. Science may give us a neurological reason why we care about species proliferation (it will go something like, “there is a brain region that makes us care about proliferation of our species.”), but why should we be limited to what our brains tend to make us think or do?
Subjective rules like these must therefore be agreed upon with the understanding that they are subject to change. Interestingly, some argue that science can answer moral questions because it can show us what “well-being” is, how we can get it, etc. But the scientific reason why we should care about well-being is nowhere to be found. The result is that we can use science to answer moral questions, but we have to first agree (subjectively) that we want well-being. Science by itself cannot answer moral questions because it shows us what is rather than what ought to be. (Actually, Sam Harris is the only one to argue that science can be an authority on moral issues; his technical faux-pas is an embarrassment to those who advocate “reason” in conduct).
But more on the idea of metaphysically constructed moral codes. What properties should this code have, and how should we go about synthesizing it? Having one fixed/rigid source as an authority for moral guidance is dangerous. Make no mistake: there must be some authority on moral questions, but it must be flexible, and adaptable; it must be able to stand the test of time on the one hand, but to be able to adjust to novel conditions on the other. This sounds a lot like the constitution of the U.S. But even with such a document as The Constitution, which has provided unity and civil progress since the country’s founding, there are some who take its words literally and allow no further interpretation; if it’s not written in the constitution, it can’t be in the law, they argue (see Strict Constructionism versus Judicial Activism). These folks also tend to be rather religious (read: they spend a lot of time listening to stories from the Bible; not to be confused with “spiritual” or of religions other than the Abrahamic ones). So while we must have a moral code, it must be flexible (i.e. change with time) and we must seek a balance between literal and imaginative interpretations, just as we do with the US Constitution.
Why and how is a rigid moral authority dangerous? Our authority must change with time because new developments in our understanding of the world must update how we interact with others. For example, if science finds tomorrow that most animals have a brain part that allows them to feel emotional pain in the same way that humans do, we will have to treat them with more empathy; research on dolphin cognition has recently produced an effort by scientists to have dolphins be considered and treated as nonhuman persons. Furthermore, if we don’t explain why we do certain things, we won’t understand why we do them and therefore won’t know why violating them is bad. This unquestionability aspect of God as moral authority or the Strict Constructionists as law-makers is what makes them particularly dangerous and leads to prejudice and ignorance. Our moral code must therefore be based on empirical research, with every rule being subject to intense scrutiny (think of two-year-olds who keep asking, “but why?”).
But why should we have a moral code in the first place? Perhaps if everyone followed a moral code of some sort, the world would have fewer injustices and atrocities. Getting people to follow a moral code of any kind is a completely different issue.
Imagine: a mad scientist with a ray gun shoots at a neuron somewhere in cortical layer IV of your visual area MT, burning it up in a matter of microseconds (just for fun, imagine also that the ray gun leaves everything else intact).
With one neuron missing, you probably won't notice any perceptual change. But what if, one by one, all neurons in are MT went AWOL? You'd be stuck with an annoying inability to visually detect motion.
Now imagine that for every cell that our fancy ray gun hits, it replaces it with a magical transistor equivalent. These magical transistors have wires in place of each and every dendrite, a processing core, and some wires in place of axon(s). Naturally, the computational core analyzes the sum of all inputs and instructs the axon to "fire" accordingly. Given any set of inputs to the dendrite wires, the output of the axon wires is indistinguishable from that of the deceased neuron.
We can still imagine that with one neuron replaced with one magical transistor, there wouldn't be any perceptual change. But what happens when more and more cells are replaced with transistors? Does perception change? Will our subject become blind to motion, as if area MT weren't there? Or will motion detection be just as good as with the real neurons? I am tempted to vote in favor of "No change [we can believe in]," but have to remain skeptical: there is simply no direct evidence for either stance.
Ray guns aside, it is not hard to see that a computational model of a brain circuit may be a candidate replacement of real brain parts (this is especially true considering the computational success of the Blue Brain Project's cortical column, which comprises 10,000 neurons and many more connections among them). For example, we can imagine thousands of electrodes in place of inputs to area MT that connect to a computer model (instead of to MT neurons); the model's outputs are then connected, via other electrodes, to the real MT's outputs, and ta-da! Not so fast. This version of the upgrade doesn't shed any more light on the problem than the first, but it does raise some questions: do the neurons in a circuit have to be connected in one specific way in order for the circuit to support perception? Or is it sufficient simply for the outputs of the substitute to match those of the real circuit, given any set of inputs? And, what if the whole brain were replaced with something that produced the same outputs (i.e. behavior) given a set of sensory inputs - would that "brain" still produce perception?