Imagine a crystal cube. Suppose this crystal is purely a static 3D entity in a 3D universe. There is no time dimension.
Like all crystals, it is a lattice of points connected by bonds (line segments) to nearest neighbors. But let's suppose, also, that these bonds are directional. The bonds aren't merely line segments, but are arrows that always point away from a particular corner of the cube. We'll call this special corner, the "origin". The opposite corner of the cube we'll call "the terminus".
If we were somehow living in this cube, we would notice that EVERY point in the lattice "attracts" arrows (bonds) from the origin side, and "radiates" arrows out towards the terminus side. Invariably.
Naturally, we would conclude that it is an absolute law of the crystal in which we live that there are always arrows going in to a point, and always arrows going out of it.
However, would we also conclude that, if the crystal is finite, there MUST be arrows entering the origin corner point of the crystal?
Would we also conclude that, in a finite crystal, at the opposite corner of the cube, there MUST be arrows exiting the terminus point?
We obviously would not.
I hope you can see the analogy. The cube is like our universe. Every point in the crystal is an event or interaction. The arrows flowing into the points are causes from the past. The arrows flowing out from a point are effects radiating into the future. The law of cause and effect is the observed law that events have causes and effects.
You should be able to see that the concept of causation is only defined INSIDE of our universe. It applies only to points within it. It has no leverage at the origin corner or the terminus corner of the cube/universe.