First off, i dont find language that suggests absolute truths helpful at all.. There are **opinions** about what the purpose of penal law should be, there arent 3 fixed reasons that are some ultimate correct answer to such a question.
Your wording is suggestive (I hope im wrong and will give you the benefit of the doubt) of an incoming toxic engagement, if that is the case I am not interested. That said I will for the moment give you the benefit of the doubt and answer you.
I can think of far more than 3 reasons for penal law. Some reaasons I can think of why a society might want penal laws (some of which i may agree with some I may not):
* Deterrant to crime - If there is a consequence and punishment to crime then it would discourage people commiting crimes. Crimes should be things that generally are harmful to society or personal rights.
* protect the public from harm - since crimes are harmful, and punishment is a deterrant to crime (as above) if effective it would reduce harm
* Rehabilitation - By arresting someone and taking away some of their freedoms allows us to force rehabilitation on a person who might otherwise not seek it. Thus allowing them to reenter society without causing harm later.
* Justice - This one (which i strongly disagree with personally) is almost spirtual in nature for many. There is just some divine cosmic rightness in the idea that someone who harms someone else gets harmed back. Its just "fair" to some people.
* Consolation to victims - By harming someone who does harm to you a victim might feel someone consoled by this fact.
* To avoid public unrest - When someone causes harm people are angry, by punishing them it may avoid things like riots or other civil unrest resulting in the lack of justice
I could easily list a dozen more reasons if i really wanted to, but those are some of the broad strokes.