Using Simple Present Tense for general truth in the past

Question

Okay, I know it may sounds silly but I just can't get this question out of my head.

So one of the functions of simple present tense is to state general truths. Like, "The sun rises from the east," or "Bikes have two tires," or the most simple thing like, "That is a book." Okay, my question is, aren't events that happened in the past are also general truths? I mean they're already happened so we can see them as facts. So why can't we use simple present when talking about things in the past?

For example. Why we write "WWII lasted from 1939 to 1945" instead of "WWII lasts from 1939 to 1945"? I mean, it's the fact (truth) that WWII lasted (i'm sticking with simple past here) from 1939 to 1945. I know we have to use simple past tense here but I want to know the reason why we can't use simple present tense.

Very silly question imo, but I'm sorry, no matter how I think (and search) about it i can't get the answer.

Answer 1

Believe or not, we do say "in 1939, a world war breaks out and lasts for six years" even though this event happened a long time ago. This is called the historical present. This grammatical phenomenon even has its own Wikipedia page. What we are doing is that we are trying to make a past situation more vivid in our mind as we speak about it. One way to achieve that is to use present-tense constructions. The page has got all the details. So, I'm not going to elaborate on it any further here. If you want to see more examples of how the historical present is used in real life, check out the Associated Press's Today in History television show. They use it a lot there.

But on a more serious note, why would you use the present tense to describe things that happened in the past even though they seem like general truths? "Seem" is the operative word here. A past event is a past event is a past event. It's, first and foremost, an event. General truths, on the other hand, are more than events. They are things that happen in general (water boils at 100 degrees Celsius, Washington, D.C. is the capital of the United States of America). An event that took place in the past stays there. WWII doesn't happen on September 1 every year. WWII is not really a general truth for that matter, it's a historical event which is a one-time occurrence. You're simply conflating two different pieces of terminology here: scientific facts and historical facts. While historical facts are in a sense as much facts as scientific ones, they're tied to a particular date on the timeline of world history which makes it inescapable to talk about them only in the past. Normally, it just semantically does not make any sense to talk about something that happened in the past in terms of the present. There's nothing else to discuss.

However, we do use present-tense verbs for general truths sometimes while talking about something that happened in the past. Both ways actually work. But this is really just an artifact of how people use and misuse tenses in general:

The Greeks actually knew that the earth is round.

The Greeks actually knew that the earth was round.

Answer 2

You may be confused about what exactly is a general truth. For example, if I throw a book into a fire, where it burns to ash, and then say:

That was a book

am I not also speaking truth? It was a book, it is not now a book.

The simple past, present, and future tenses merely establish the time frame. Otherwise it's the context that tells us if something is a "truth".

The sun will rise tomorrow, as it does every morning.

At its peak, the Roman Empire stretched from Britain to Egypt.

She baked together three varieties of apples to make her famous pies.

I think perhaps what you are talking about are truisms, a common statement that is obviously true, independent of time frame:

Apples are red

The ground is wet after it rains

and so on. In this case, given no other time frame, use the simple present by default.

A penny saved is a penny earned.

Once you add the time frame you have to decide whether it is better to express it as true in the past, the present, or the future.

In the early 17th century, when the phrase was coined, perhaps, yes, a penny saved was a penny earned. Today, many pennies are more valuable for their copper than as actual currency.