I'm doing a series in Sunday school with high school students about the philosophy of Christian ethics. We're looking at why certain actions are wrong based on teleology.
Today we discussed drugs and alcohol. We began by defining a human being with Aristotle's definition, "Man is a rational animal." I asked the students what makes man different from animals. They gave great answers:
The problem with drunkeness and "getting high" is that it reduces our ability to engage in those functions unique to humanity. When we're drunk go from being a "rational animal" to being merely an "animal." Our freedom of will is handicapped (especially with drug addiction), we lose our skills, we slur our speech, our inhibitions fall away, etc. The imago Dei falls under a shadow and we sink not heavenward but back to the earth from which we sprung.
This technique is rather potent with teenagers. Sin is not merely wrong because God arbitrarily decided to proscribe certain acts that appear to be really cool and fun. Rather, they are wrong because they destroy His purpose for us to be truly beatified and sacred.