a challenge to Erin's rule

[christation]

According to Erin's Banana Rule Exceptions, we often use part of without an article before it. For example, oxygen is part of water. However, I found a part of is often used too. For instance: It is a part of the story. So, I think, there are no differences between the two conditions. What do you think of it?

Second, according to Erin's quantifier + of + determiner + noun, as a quantifier, part(of) will be used like this: Part of the meat was spoiled. But I found another correct example: The calliope was a part of fairs. Or : a part of modern education.
That's to say, these sentences can exist without determiners!!!!!!!!!

Come on! Who can tell me why? I'm really confused.

[Erin]

Chris, this is language we're talking about, not math or computer science, and it can't always make sense.

In many cases, two cases may both be correct. Another similar case that comes to mind is the exception about not needing to use determiners with professions: Poet and author Maya Angelou... Inventor Thomas Edison... President Bill Clinton... Film actress Lucy Liu... Webmaster Erin Billy... TOEFL Guru christation... etc.

All of the above would be correct WITH deteminers as well. This is a very important concept in grammar, Chris: just because a determiner is not necessary doesn't mean that it is incorrect with one. In many cases, these things are optional, and may even some subtle change in meaning.

[christation]

Hi, Erin. Thank you for your reply. And it's almost 24 o'clock!
I really appreciate your help.