You seem to be using the term "Naturalism" in the context of atheism and the idea that only this universe of mind, matter, energy, cause and effect, nature, etc, can exist.
Well we do think we know that these things exist. Most theists and non theists seem to accept that these exist. And so they are a common currency (if you like), that we share.
But for "things" beyond this universe?
Well they might exist. But then again, they might not exist.
Any assertion that a specific entity or a specific realm does exist beyond this universe, is more likely to be wrong than the assertion that it does not exist.
However, if dimensions beyond the four we think we know of, do exist, then perhaps it's more of an open question. However it remains hard to know exactly what does exist out there in those possible other dimensions of mathematics and physics, and so assertions which claim to know, are still likely to be wild guesses.
So, as to the question of what lies beyond the universe, I think the best answer is, "I don't know, that's if it's possible to have a 'beyond' the universe". Nevertheless, if you think you have had a signal from out there then two things:-
1) Don't expect to convince any one, unless you can do better than "you cannot prove that I'm wrong".
2) Expect someone else to claim a signal from out there, and to claim that your signal is wrong.
The definition of Naturalism was the focus of an earlier thread: in order on this thread to know what has limits.
Naturalism is based on what we know through our 5 senses, mental capability/intelligence, and the Scientific Method. In this broad definition would include the various properties of the physical realm, and what we have learned through careful use of science.
Naturalism is the view that a Creator or God had not and is not needed to explain this physical world we live in. From sickness, to events like lightening, to the physical history of the earth with what we have learned through elements of geology, like isotope geochemistry, sedimentology, paleontology, tectonics, and the like.
So the foremost base of our discussion centers on Naturalism. From this base, which many Naturalists think and live, we can then discuss its limitations. Including the lack of various evidences Naturalism has.
I appreciate many points in your reply about the possible limits Naturalist have. And agree other people will have the same limitations.
What is beyond the physical is an open question, particularly for Naturalists. That is why I referred Naturalism to be narrow and confined, since the evidence needs to be through the Scientific Method. Not that the Scientific Method process is wrong. In the present physical world it has and will continue to provide many benefits.
In reply to a signal that is beyond our present natural world your point is clear and right. Why I have limited the topic to Naturalism and its limitations is to discuss this possible signal, if it exists, for another thread. Like with Naturalism, until we know what it is we will have a problem understanding if it has any limitations. In turn, until we understand the limitations of Naturalism we may not understand how something beyond Naturalism detection exists.
In the limitations to be learned - once a true Naturalist - I've tried to present the most basic and important. Being a regular person, being composed of the elements, Point 1 is definitely ultra basic. Point 2 is also ultra basic, particularly for Naturalists. But what appears very basic in some of the other Points, many may still need to ponder. I'm not trying to force any viewpoints. But the "ramifications" behind these seemingly also ultra basic items has major implications. One is Point 7. No doubt there will be many that will disagree. They will state why. But will they be right to say they do not walk by faith? We need to understand the limitations of Naturalism before any signal, higher life, and the like discussion.
