the devil, via instapundit

, brings up a question that should be considered when reading any internet forum:

The problem ... is this: How does one tell, and tell about, the difference between right and wrong? Why ought one - a person or a society - do any particular thing rather than any other? How can one ground any statement in the form "It is right to do X" in anything firmer than the quicksand of bare reiterated assertion? As intellectual puzzles go, this one is a lulu... no one else has come up with a satisfactory solution, from the beginning of the world to the date hereof.

you should read The Book for the answer.