"There seems" or "There seem"

文法は苦手で余り勉強しないのですが（だから苦手chicken and egg）、ネイティブでも動詞に ”s” を付けるべきかどうかでもめることがある様です。
　“seem” か “seems” かで夫ともめた奥さんからの投書です。

Q. Here's our latest quandary; it regards the following quotation attributed to Abraham Lincoln: "No matter how much cats fight, there always seem(s) to be plenty of kittens."
My husband thought it should be "seems," but "seem" sounds OK to me, but I don't know why. I find it quoted on the Internet both ways, which doesn't help matters! -- Sharon Hauser, San Jose, Calif.

なんだか、受験英語、TOEICに出そうな問題ですね。インターネットで調べると、確かにこの引用文、"No matter how much cats fight, there always seem(s) to be plenty of kittens."はリンカーンの言葉として掲載されています。

ちなみにこのネイティブの質問に対する回答、"seems" と "seem" のどちらが正しいかも少し長いですが参考に下に示します。

A. Screeching grammarians -- and even some husbands and wives -- might fight like cats over this distinction, but there's no need for such caterwauling.

In sentences such as this one, where "there" functions as an anticipatory or "dummy" subject, the true subject of the verb is the noun following the verb. So we say, "There always seems to be a problem" or "there always seem to be problems." So far, so good.

But Abe has thrown us a curveball by choosing a subject ("plenty") that can be either singular or plural, depending on its meaning. While you would say, for instance, "there always seems to be plenty of money" because here "plenty" means a single amount, you would also say "there always seem to be plenty of kittens" because here "plenty" means many individual items.

So the prepositional phrases following the true subjects ("money," "kittens") enrich the meaning and help us determine the singularity or plurality of "plenty." Take them out, and you have to determine the choice of verb by context alone, e.g. "Do we have enough food?" "There seems to be plenty," and "Do we have enough chairs?" "There seem to be plenty."

つまり、"There" は仮の主語で、動詞(seem)の実の主語は"to be" の後に続く名詞なのですが、投書の例がネイティブにも悩ましいのは、名詞に "plenty" が付いているので名詞が単数なのか複数なのか判断に困るという例でした。従って、回答者の助言は "plenty" を除き、名詞が単数なのか複数なのか判断しなさいでした。