Reasons for Action: Justification vs. Explanation (Stanford Encyclopedia of Philosophy/Spring 2016 Edition)
Modern philosophical literature distinguishes between explanatory reasons and justifying reasons. The former are reasons we appeal to in attempting to explain actions and attitudes. The latter are reasons we appeal to in attempting to justify them. Here is Galahad sticking pins in the Paraguayan flag. Why would he be doing that? Here's a possible explanation. Galahad has a murderous hatred for Paraguayans. He believes they are evil and wishes to destroy them. A well-intentioned acquaintance, seeking to render his murderous bigotry harmless, has persuaded him to believe the superstitious falsehood that the most efficient way to destroy Paraguayans is to obtain a Paraguayan flag and stick pins in it. This he is now doing. We ask what reasons, if any, there are for Galahad to be acting as he is? And it is natural to answer that there are no reasons for him to be doing so. There is no story to be told to make good normative sense of what he is doing; for what he is doing makes no good norm