Can someone help me define Western Civilization?

[Dachs]

Well, I mentioned the Western Roman Empire because Europe seems to have come from two halves after the splitting of the Empire. A Western Roman one and an Eastern Roman one. And the remnants of the Western Roman Empire, aka, France, England, Italy and later Spain versus the remnants of the Eastern Roman Empire in two cultural spheres.

But those differences had little to do with any difference between the WRE and ERE. What you're really looking at is more of the fallout from the reign of Ioustinianos, and the epochal shifts in ideology of rulership in the West that date from around 600. I would recommend here Guy Halsall's next book, but it hasn't come out yet. (Seriously. There's a Facebook group devoted to his worship, and if I had fb I would totally join it.)

Of course, I have to agree with you as stated before, I think this whole "defining western" civilisation thing quite silly since the best definition seems to encompass half the planet of vastly different things and we should just get rid of it. Even in Europe, at best, you have Latin-derived Europe and Byzantine derived Europe with countries like Romania and Bulgaria that straggle in the middle. FYI, I don't they are mutually exclusive. Just very different ends of the same spectrum.

Why semi-valid?

I think that they are semi-valid grounds partially because some of them are factually incorrect, and partially because I think that the entire concept is a farce.