I want to know why some things are unclean (najasat) in Islam. I ask this question from some people they believe cleanliness helps human avoid microbes. But my teacher tell me it isn't main reason and there is philosophical reason for them.
He says dog is unclean because it is symbol of Wrath (Ethics dogs like) and there is many dogs in people life. He is citing the some example: a wolf is very wilder and rougher than dog but it is Rare in people life so it isn't unclean same dog.
He says pigs is symbol of lechery and libido.
Corpses are a symbol of Low-spirited because we should prevent bad friend or people. My teacher's reason: Martyr isn't unclean because his symbol of Dedication.
. . .
Our teacher told me when we confront uncleanness we should Inculcate to self that prevent from doing them based on its symbol.
He told me when we touch unclean thing we should clean my self because it is a symbol of avoiding the indecency based on its symbol.