You're arguing as though the phrase 'social contract' refers to a literal contract, which isn't even slightly true.

Of course it doesn't refer to a literal contract. But a non-literal contract has no binding, so under what crazy-land definition of justice can the state use it to deem its actions of taxation, conscription, etc as just?

It really sounds like you have a mental model of the 'social contract' concept that isn't aligned with what it means for everyone else. To be clear, it says that we (possibly tacitly/implicitly) agree to give up some freedoms to the government in exchange for their governance/defense/etc. It has nothing to do with the enforceable contracts and things you sign. It just frames the relationship between government and constituents in terms of an agreement.

So if we give up certain freedoms in this agreement (such as the 'right to not be taxed'), then it's not unjust - we have (tacitly, implicitly) consented to this. It's true that you the individual might not have consented, and might not have the means to leave if you don't like it. But the collective is consenting, and can change the constitution if they change their mind.

So taxation is not inherently unjust if the state's constitution says it can tax you by definition. You might think the social contract that we're using is bad, or that the constitution is bad, and that's fine, and you can change it democratically if enough people agree with you. But 'unjust' doesn't really work.

> if the state's constitution says it can tax you by definition

I wasn't aware that the state defines what is just and what is not. Does that mean that there are no unjust laws?

The constitution defines what it just. Laws can be unjust.

The constitution is a law. It is the supreme law, by its own definition.

Just as an exercise, do you think you can write down my counterargument? It's not hard to see what I'll probably say.

edit: here, I'll help you. For part (a) of this question, list four different meanings of the word 'law', and give an example of each. For part (b), describe what the word 'just' means when applied to each definition from part (a). (Hint: they are all different.)

You first.

It's not a contract at all - in much the same way that the Democratic Republic of Korea is not a Democratic Republic. It's a weasel word used to give the appearance of consent when in-fact no consent has taken place.

Taxation is not theft because taxation is a legally established process for funding a society, and theft is the unlawful taking of something without permission.

You do not need to personally consent to or agree with all laws for them to apply to you.

You are also free to make taxation a point of civil disobedience, if you feel that strongly that it is immoral.

You are free to start a movement to eliminate all taxation, and if you succeed in having it become the law of the land, then taxation will no longer exist, of course, but it would still not be theft under any circumstances.