(Quora) Eric Lander chose lectures that would give the audience a perfectly relevant introduction to Biology, touching on topics in his research in the Human Genome Project.
Where is the definite article? Should not it be the topics, because these are the exact topics
Adding the definite article would imply that the introduction would be touching on all topics that are covered in the mentioned research.
Without the article, or rather with the indefinite plural article (which in English happens to be a null article), the writer indicates that the introduction will touch topics from the research, but it may not be all of the topics in the research.
Maybe another example will make it a bit clearer. I'm on apples today somehow, so bear with me.
I like to eat apples. I know a farmer who grows them. Now, if I eat an apple, and it comes from that farmer:
The apple I ate was an apple from the farmer.
If I eat several apples, both the definite and indefinite article change to the plural:
The apples I ate were apples from the farmer.
If in any of the sentences I would use the definite instead of the indefinite article, the meaning of the sentence would change dramatically:
The apple I ate was the apple from the farmer.
Either the farmer only had one apple, or possibly, I had earlier obtained several apples, but only one was from that farmer.
The apples I ate were the apples from the farmer.
Now I ate all the farmer's apples (burp), or indeed, I had earlier obtained several apples, some of which came from the farmer, and I ate those.
Putting articles is always tricky and even learned people miss them sometimes.
Placing the definite articles reflects that he's very clear about the topics he'd be covering or touching on. However, practically it's not possible as there could be innumerable topics to cover.
Remember, if you want to specify anything general in mass, drop the definite article the. I had read this example somewhere which is very useful.
I know that elephants are dangerous - would imply elephants in general.
I know that the elephants are dangerous - would imply that elephants of a particular group (maybe, the elephants in this zoo or area are dangerous).
Considering this, the author wanted to talk about topics covered in his research in general and not the topics those are countable and given names to.
Note: One would also argue that the topics is correct as well. I don't deny. I'm covering the topics I have prepared in this presentation is fine. However, the site is Quora and there you don't expect the content to be flawless.
