[jmyeet]

So this seems like a better definition until you run into a problem, which you do pretty quickly: "casuality" isn't the easiest thing to define.

The best definition I think I've seen is to view the universe as a partially ordered set of events, meaning that you can only order events (in time) if they're within each other's cones of causality. Outside of that you cannot say which happened first. That's the partially ordered part.

But even that is incomplete and arguably even self-referential. What's a "cone of causality" (without relying on causality)?

Also, there's the issue of what exactly time is and whether events are time-symmetric or not. Many physicists seem to view time as an emergent rather than fundamental property of our Universe.

[cypherpunks01]

Causality is *bangs hammer on bell*

Time is a relationship between clocks.. beyond that, yes, it's hard to say exactly.

Time seems to be what prevents everything from happening at once.

[hinkley]

Without time does causality exist? Does anything happen at all? What is it to 'happen' except that something was one way and now is another?

I can't even describe 'happen' without using verb tenses, which represent time.