I didn't say "miracles;" I said "messengers."What you said is true, which is why miracles in the past are not guidance for the future or present, but rather Quran says:
And the disbelievers say why a sign not revealed regarding him, you are only a warner and for every people, there is a guide!" (13:7)
A current guide showing miracles, seeing those signs by his hands would not be circular reasoning and is in fact, what Quran means by his proof.
That being said, the whole idea of "miracles" is inconsistent nonsense. Here's the problem:
- a miracle is something that happens despite not being possible by natural laws.
- but natural laws are inferred from observation of what happens.
- this means that everything that happens is natural.
- so a miracle that happened would both be natural (since it's a thing that happened, and therefore form an observation that would be incorporated into natural laws) and not natural (by definition).
... so when people talk about "miracles" happening, they may as well be talking about square circles.
Demonstrate God with empirical evidence, just like anything else. Build up a set of evidence so strong that the universe makes much more sense with God in our model than without him.