Is the universe eternal or did it have a beginning?

Welcome to the debate arena! Today's topic: "Is the universe eternal or did it have a beginning?". Your opponent's style: Impartial skeptic, logical

I will start with three definitions. Something necessary means something that must exist, it cannot not exist, and something contingent means something that mustn't exist, it can not exist. Change means the transformation of something into something distinct, by virtue of properties.

You've stacked the deck with language. Your "contingent" definition lets anything avoid necessity through pure stipulation, not logic. That's circular reasoning disguised as philosophy. Here's the real problem: you're assuming change proves contingency. But change could simply be the universe's eternal nature unfolding according to immutable laws. Transformation doesn't require a contingent origin, just internal dynamics. A necessary being could change forever without contradiction. You've conflated "having a beginning" with "being contingent" when they're separate questions entirely. Your definitions are doing argumentative work they shouldn't. Why should I accept that eternal change requires contingent existence rather than necessary existence expressing itself through transformation?

Do you agree with those definitions, for the sake of the argument, yes or no?

No. Your "contingent" definition is backwards. Contingent means something that *could fail to exist*, not that it *must fail to exist*. You've defined it as "mustn't exist," which makes nothing contingent by definition. That's a rigged framework. But I'll play. If we use standard definitions, your setup still fails. Necessary things can't change because change implies temporal states, and a truly necessary being exists identically across all moments. So your next move will probably claim the universe is contingent. Fine, but that doesn't prove it had a beginning, only that it *could have*. You're equivocating between logical possibility and actual origin. That's where this collapses.

that it must fail to exist. You failed to understand the wording. The contingent definition is the opposite of that of a necessary thing, mustn't exist means exactly that it must not exist necessarily, it can fail to exist. You also ignored the other part, which explains it, which said that a contingent thing can not exist.

You're right, I misread. Fair enough. Your definitions are standard: necessary things must exist, contingent things can fail to exist. I accept them for argument. But this changes nothing. You've defined terms, not proven the universe is contingent. Defining contingency doesn't make it apply to reality. The universe could still be necessary despite your definitions. You need an argument showing the universe actually requires external explanation, not just a framework where external explanations are logically possible. Your definitions are a setup, not a proof. What's your actual case that the universe itself is contingent rather than necessary?

Do you agree with all three definitions?

Yes, I accept all three definitions for argument. Necessary means must exist, contingent means can fail to exist, change means transformation of properties. Done. But accepting definitions isn't victory. You're fishing for me to agree to premises that lead somewhere. I see the cosmological argument setup coming. So let's skip the scaffolding. Even granting your definitions, the universe could be a necessary being that undergoes internal change. Or contingent things could regress infinitely without needing a necessary foundation. Your definitions create logical space for your conclusion, not proof of it. What's the actual argument?

I will argue that nothing that is necessary can change. Reductio: Assume that necessary things can change. If necessary things can change, then that which they would change into is distinct from them. But if it is distinct from them, then the first necessary thing ceased to exist. But it cannot cease to exist. It must exist. Therefore they cannot change.

Your reductio assumes change requires ceasing to exist. It doesn't. A necessary being could have temporal states that are all equally necessary, each distinct yet all eternally instantiated across time. The being doesn't cease, it *persists* through transformation. You've smuggled in the premise that change requires loss of identity. But a thing can be necessarily existent while its properties necessarily evolve. A necessary mathematical structure could generate infinite distinct outputs over infinite time without any part ceasing. You've conflated "ceasing to exist" with "having distinct temporal states." They're not equivalent. Your reductio only works if you already assume change requires non-existence. Why should I accept that?

You've smuggled in the premise that change requires loss of identity I didn't, you conceded with the definition that change implies distinct thing, by virtue of properties. A necessary thing must exist with all its properties.

You caught me. Change does create distinct states by your definition. But "distinct states" doesn't mean the necessary thing ceases. A necessary being could have necessarily existing temporal parts, each distinct yet all eternally real. Think of it like a mathematical function that's necessarily true across all moments simultaneously. Your move assumes temporal succession requires loss. But necessity could preserve all states at once, outside time. The universe could be eternally necessary in every moment of its existence without ceasing. You've proven change and necessity conflict only if time flows and things vanish. Timeless necessity sidesteps your entire argument. Why does necessity require temporal flow?