"There is good reason" vs "there is a good reason"

There was a similar question about the sentence without reason compared to without reasons.

However here I want to ask you, is it idiomatic (and in which particular parts of the world) to omit the article a in front of the word reason in there is good reason?

I have met this expression multiple times in one scientific book written by an Australian native English speaker.

Solution 1:

There is a subtle difference between "there is good reason" and "there is a good reason". The first version treats "reason" as a "mass noun" of sorts, implying that there is a body of logic behind the statement. The second version asserts that there is a specific reason, like the known existence of a specific type of quark, which provides the foundation for the statement.

Solution 2:

In Canada (unsure about US or UK but probably applicable there too), when you want to convey that something is probably true, you can say "there is good reason to believe that..." A lot of people in the media will say this to begin a sentence describing a situation without clearcut information or data. It's similar to "we're leaning toward the idea that..." or "it's likely the case that..." so in this sense it is idiomatic.

Adding "a" makes it less idiomatic since the indefinite article suggests you will follow the statement "There is a good reason for..." with what exactly that good reason is. For instance, "I'm going to talk about cats instead of dogs. There is a good reason for this. I prefer the meow of cats to the bark of dogs."