It's not really a historical question, but one of ontology. Does changing brown for patent malt change the essential nature of a porter? Which is to say, a dark beer of the style made in the UK, made like most UK beers of a combination of UK-style pale malt and cereal adjunct, with UK style top fermenting yeast and UK-style hops. All beers made in the region are made using similar styles and methods, so the "Irish" type is at best a subtype, and one I'm not convinced exists, given that brown malt was phased out almost entirely over the next few decades. [My bold. Incidentally, "ontology" is concerned with the nature of being.]There's actually a lot more, including a nice contribution from the Beer Nut. I won't re-litigate the arguments here--you can go have a look and see where you fall on the (unresolvable) debate.
|Source: Beer Growler/Juliano|
It's relevant partly as a check against hyper-geekiness. When you spend a lot of time studying, brewing, and drinking beer, you tend to see subtle differences as gaping chasms. But I spend a lot of time drinking beer with non-beer geeks, and I sometimes have the emperor's-new-clothes experience when I'm attempting to justify how one beer is meaningfully different from another. To beer geeks, yes, the distinction between San Diego IPA and Portland IPA has meaning. To everyone else, this is pointless hair-splitting. Unless we want beer to become a tangled world of byzantine complexity, it's wise not to ignore that view. The everyman rule is a good check on over-thinking style.