All things are causally related, directly or indirectly. And being causally related involves being logically related.
Consequently, everything in the universe is related internally to everything else.
But is everything really related causally to everything else?
If they are not, it could only be because either some events are not caused or that if all events are caused, they are not all related causally to all the others.
In fact, the ulitmate components of matter are not governed in every detail by causal law.
There is the Heisenberg indeterminacy principle, that a particle may have position or velocity but not both in any exact sense.
There is also the view that the macroscopic objects with observable behavior are all enormous aggregates of sub-atomic particles, that the regularity of their behavior is merely the statistical stability displayed by other large aggregates, and that this regularity is as consistent in the one case as in the others with caprice among the ultimate components.
The theory that there is something in the situation of a radium atom determining it to break up at one moment rather than another is without evidence.
Well, some physicists have not been persuaded that the new results point validly to any suspension of causality, such as Einstein, Planck, Lodge, and Rutherford. So whichever side you take, you will at least have it on some good authority.
Also, some who have examined the Heisenberg indeterminacy principle believe it confuses indeterminacy in our knowledge with indeterminism. The use to which the principle of indeterminacy has been put is largely due to an ambiguity in the world 'determined'. In one sense a quantity is determined when it is measured. In the other sense, an event is determined when it is caused.
The principle of indeterminacy has to do with measurement, not causation. The velocity and position of a particle are declared by the principle to be undetermined in the sense that they cannot be accurately measured. This is a physical fact causally connected with the fact that the measuring is a physical process which has a physical effect on what is measured. There's nothing in the principle of indeterminacy to show that any physical event is uncaused.
So it would be precipitate to assume the principle of causality has been falsified. Of course you don't prove it true by showing that certain objections to it are questionable. But since apart from such objections, the principle holds the field, a constructive argument for it is perhaps unnecessary at this point.
But granting universal causality, there are areas of causal influence that are closed to each other. So what is happening now in the sun can be neither cause nor effect of anything now happening on earth, because no causal agency, not even gravitation, can travel faster than light, and it takes light an appreciable time, about eight minutes, to make the journey from sun to earth.
There's nothing in such facts to challenge universal causality. Everything is not directly connected to everything else, so that you could pass from any event to any other by following a single line of causation forward or backward. But everything is connected directly or indirectly with everything else. Events now happening in the sun are traceable to causes occurring only a few minutes ago which in turn did affect the course of events on earth.
So events in the two regions, even when neither is the cause of the other, are connected through common causes. And there is no region or event that is cut off from any other. Every body pulls every other towards it, no matter how distant it may be. Newton's apple not only exerted its pull on the earth, but every star in the sky, and the motion of every star was affected by its fall. We cannot move a finger without disturbing all the stars.
So the causal relation is universal, and causal relation includes indirect causal relation. Consequently, every existing thing is causally related to every other thing.