Is there philosophical reason for unclean things (nejasat) in Islam?

Question

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.
For example:

1. 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.

2. He says pigs is symbol of lechery and libido.

3. 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.

Answer 1

Islam means surrender and submitting to Allah, compliance with his orders and avoid prohibitions, knowing that Allah only commands what benefit us , and forbidden what is evil. After submitting to that, it's ok to search for the wisdom of the do's and don'ts, but I’m not comfortable with people try to add extra (invented) justifications (i.e philosophy) to Sharia rules, to grant them acceptance or to show a deeper dimension in it, for example “najasat”, Allah said:

makes lawful for them the good things and prohibits for them the evil 7:157

Science may prove that “najasat” are harmful, and there are intangible harm (which science cannot prove) but the prophet (PBUH) told us about, such as angels will not enter a house contains a dog, but what is the evidence for what your teacher said? There is no scholar, Hadith or Quran establishes that a dog is symbol of Wrath! pig is symbol of lechery or Corpses are a symbol of Low-spirited

Islam is the religion for all humans, the very simple person who lives on a mountain and never saw modern life should be able to understand it, and he does not need to be a philosopher to explain the sharia .

What your teacher said is simply wrong, because it lacks evidence from the Legitimate sources as well as not being logic, following his logic we can claim anything, I can say cats are symbol of stealing but that is not going to make it “najas” as dogs, because Sharia did not say that. So his opinion can be considered a personal opinion but not good enough to teach it.